LIBRARY 

OF    THE 

UNIVERSITY  OF  CALIFORNIA. 
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'   • — " - -  *"• "™"  ' - • 

Architects'    arid    Engineers' 
Hand-Book   of 

1%je*Inforced  Concrete 
Constructions 


J.  MENSCH,  C.  £. 


Price,    $2.OO 


Cement  and  Engineering'  News 
CHICAGO,  ILL. 

..      - .  .      ......   .     . 


ARCHITECTS'   AND  ENGINEERS' 
HAND-BOOK  OF 

RE-INFORCED   CONCRETE 
CONSTRUCTIONS. 


Giving  in  plain  and  simple  language  the  leading  principles 
and  applications  of  this  modern  construction. 


WITH  NUMEROUS  ILLUSTRATIONS  AND  TABLES. 


BY 

L.  J.  MENSCH, 
CIVIL  ENGINEER  AND  CONTRACTOR. 


Published  by  the 
CEMENT  &  ENGINEERING  NEWS, 
162  La  Salle  Street, 
CHICAGO,  ILL. 


GENERAL 


Copyright,    1904. 

by 
WILLIAM  SEAFERT. 


INTRODUCTION. 

The  information  given  in  this  Hand  Book  is  drawn 
largely  from  the  writer's  own  experience  as  Designer, 
Consulting  Engineer  and  Contractor  for  re-inforced 
concrete  constructions. 

In  the  practice  of  his  profession  in  various  parts  of 
the  country,  he  has  been  brought  in  contact  with  archi- 
tects, engineers,  contractors  and  capitalists,  interested 
in  this  new  method  of  construction.  These  clients  and 
others  have  from  time  to  time  propounded  numerous 
pertinent  and  carefully  considered  questions,  relating  to 
the  essential  features  of  re-inforced  concrete  construc- 
tion, especially  as  compared  with  other  materials  and 
forms  of  construction.  These  questions  and  the 
writer's  answers  were  uniformly  reduced  to  writing, 
classified  and  preserved  and  now  form  a  portion  of  this 
Hand  Book,  together  with  other  matter  bearing  directly 
on  the  subject. 

The  writer  has  aimed  to  treat  the  subject  in  plain, 
simple  language,  entirely  free  from  higher  mathe- 
matical calculations. 

The  mathematical  side  of  this  subject  will  be  exhaus- 
tively treated  in  the  more  extensive  treatise  now  under 
way  by  E.  Lee  Heidenreich,  to  be  published  by  the 
Cement  and  Engineering  News. 

Re-inforced  concrete  is  the  ideal  building  material 
of  the  future  and  must  in  a  great  measure  displace  the 
older  materials  of  construction  upon  its  intrinsic  merits. 

124959 


Re-inforced  concrete  construction  is  at  the  present 
time  little  understood  by  our  most  competent  engineers 
and  architects,  due  simply  to  the  absence  of  suitable 
literature  in  the  English  language  on  the  subject. 

If  this  Hand  Book  becomes  the  medium  of  convey- 
ing the  desired  information  to  the  architects  and  en- 
gineers and  thereby  promoting  the  more  general  use  of 
this  new  method  of  construction  by  the  public,  the 
writer's  aim  will  have  been  accomplished. 


INDEX. 


Arched   Bridges 180 

Arched    Culverts 169 

Arches  for  Halls 177 

Basement  Walls 91 

Beams    14 

Bins    151 

Bridges    182 

Coal  bins  -. 145 

Cement  finish 46 

Cement  specifications.  212 
Centering  for  beams. .  17 
Centering  for  columns  55 

Cisterns 137 

Columns    53 

Considere  columns  . .  62 
Concreting  in  hot  or 

cold   weather 45 

Chimneys    170 

Cost  of  skeleton  build- 
ings     112 

Culverts    169 

Dams   132 

Deflection      of      steel 

beams   114,  115 

Docks 78 

Domes    176 

Elevator         enclosure- 
walls    101 

Elevators    (Grain    and 

Storage)     145 

Factories    48,   50 

Finish  of  floors 45 

Finish  of  walls 88 

Finish  of  tanks   .        ,   137 


Fire   tests 118 

Flumes    162 

Floors    35 

Floor  slabs 35 

Floor'   loads 50 

Footings    67 

Foundations    67 

Foundries 48,  50 

Girders    14 

Girder    Bridges 186 

Grain   elevators 145 

Granolithic   finish ....     46 

Halls    177 

Hollow  floors 38 

Harbor   work 78 

Ingalls     Building 109 

Jetties    78 

Lintels  100 

Mattress    71 

Marine   work 78 

Patent   bars 206 

Piers    78 

Piles    75 

Pipes    156 

Prismatic       side-walk 

lights    179 

Properties  of  combina- 
tion of  concrete  and 

steel   124 

Rafts    71 

Railroad  ties 181 

Retaining   walls 128 

Reservoirs    137 

Roofs   4S 

Safety     of     Armored 


INDEX. 


Concrete  Bldgs 126 

Sewers   165 

Sheet   piles 77 

Skeleton    buildings...     98 

Slabs    35 

Specifications  for  rein- 
forced concrete  work  208 
Specifications    for    ce- 
ment       212 

Standpipes    137 

Stairs    91 

Steps    93 

Tanks    1   137 

Table  of  loads  on  floor 
slabs    35,  38 


Test  of  reinforced  con- 
crete beams 19 

Test  of  reinforced  con- 
crete columns 55 

Vibrations  of  Rein- 
forced Concrete  floors  IIS 

Walls,  reinforced  con- 
crete    81 

Walls  of  concrete 
blocks  100 

Ware-houses    112 

Water   mains 156 

Weight  of  •  concrete 
floors  49 

Wharves  78 


INDEX  TO  ILLUSTRATIONS. 

Fig.     7  Test  of  girder,  Salvation  Army  Bldg.,  Cleve- 
land,   0 20 

Fig.     9  Test  of  Girder,  Davis  Sewing  Machine  Co/s 

Bldg 22 

Fig.  11  Balcony  Girders,  College  of  Music,  Cincin- 
nati,  0 25 

Fig.  12  Eoof  and  Balcony,  College  of  Music,  Cincin- 
nati,  0 I 24 

Fig.  13  Test  Load  of  77,000  pounds,  J.  H.  Day  & 

Co.'s  Foundry,  Cincinnati,  0 26 

Fig.  14  Lintel  of  33  ft.  span,  Cincinnati,  0 27 

Fig.  17  Test,  Champion  Ice  Co/s  Bldg.,  Covington, 

Ky 31,  32 

Fig.  19  Test,  McKinley  High  School,  St.  Louis 33 

Fig.  20  Eoof  and  Balcony  Girders,  McKinley  High 

School,    St.   Louis 34 

Fig.  24  Test  of  hollow  floors,  Sheldon  residence,  New 

York  City 39 

Fig.  26  Hotel  Gallia,  Cannes,  France 41 

Fig.  27  Hansa   Haus,   Dusseldorf,   Germany 42 

Fig.  28  Electric  Fountain  and  Cascade,  Paris  Ex- 
position      43 

Fig.  31  Shed   Eoof 47 

Fig.  32  Foundry,    Hull,    England 48 

Fig.  33  Foundry  Building 49 

Fig.  38  Salvation  Army  Bldg.,  Cleveland,  0. .  .56,  57,  58 

Fig.  41  Concreting  of  Girders,  Floors  and  Columns.  59 

Fig.  45  Sugar    Warehouse 64 

Fig.  46  Cold    storage    warehouse    and    power-house, 

Southampton,   Eng Go 

Fig.  53  Warehouse,  New  Castle-on-Tyne, 69,  72 

Fig.  58  Driving  of  Eeinforced  Concrete  piles TJ 

7 


8  INDEX    OF    ILLUSTRATIONS 

Fig.  57  Retaining  bank,  Southampton,  England.. 78,  80 
Fig.  60  Barge-quay  and  jetty  in  course  of  construc- 

ton 81 

Fig.  62  Woolston  jetty 83 

Fig.  63  Dagenham  jetty 84 

Fig.  66  Apartment  and  office  buildings,  Paris 86 

Fig.  67  Fire-proof   Archive   Buildings,   Paris 89 

Fig.  69  Stairs  and  cable  drive 92 

Fig.  70  Fire-escape,    Strassburg 93 

Fig.  71  Staircase,  Salvation  Army  Bldg.,  Cleveland  94 

Fig.  72  Staircase,  Ingalls'  Building,  Cincinnati,  0.. .  95 

Fig.  73  Looking  down  10  flights  of  stairs 93 

Fig.  74  Staircase  of  a  department  store 97 

Fig.  75  Skeleton  of  a  flour  mill 98 

Fig.  76  MacDonald  &  Kiley's  Shoe-factory,  Cincin- 
nati      99 

Fig.  78  Flour  mill,  grain  elevator'  and  smoke  stack, 

Brest,  France 102 

Fig.  79  Cotton  spinning  mill,  Strassburg,  Alsace.  . . . 

103,  104,  105,  106 

Fig,  84  Audit  office,  Paris,  France 109 

Fig.  85  IngalFs  Building,   Cincinnati 110 

Fig.  86  Factory  building 113 

Fig.  88  Grand   stand,    Cincinnati 119 

Fig.  89  Flour  mill  and  grain  elevator,  Swansea,  Eng- 
land      121 

Fig.  96  Design  for  the  Nile  Dam  at  Assouan 135 

Fig.  97  Tank  at  Bournemouth,  England 133 

Fig.  98  Tank,    Scafati,   Italy 140 

Fig.  99  Water  tank  with  hollow  walls 140 

Fig.  100  Water  tanks 141 

Fig.  102  Reservoir  Lausanne,  Switzerland 143 

Fig.  103  Wine  vats 141 

Fig.  105  Swansea  Elevator 146,  147 

Fig.  109  Coal   bins 152,  154 

Fig.  Ill  Coal  breaker  stations 153 

Fig.  112  Storage  bins,  Hecla  Portland  Cement  Co.. .  155 
Fig.  117  Manufacture  of  Pipes  in  movable  works.  15 8,  159 

Fig.  124  Flume,  Simplon  Tunnel 162,  163 

Fig.  127  Power  canal  anl  spillway 164 


INDEX    OF    ILLUSTRATIONS  9 

Fig.  128  Section  through    17   foot    tunnel,     Paris, 

France    165 

Fig.  132  Chimney,  Los  Angeles,  Cal 171  to  173 

Fig..  135  Limekiln  174 

Fig.  .136  Dome,  Cairo,  Egypt 175 

Fig.  137  Hall  of  81  ft.  span 177 

Fig.  138  Railroad  guard  tower 178 

Fig.  139  Reinforced  concrete  side-walk  lights. .  .179,  180 

Fig.  141  Railroad  bridges 183,  184 

Fig.  143  Girder  bridges 184,  185,  186,  187 

Fig.  149  Tubular   bridge 188 

Fig.  150  Covering  of  Subway,  Paris,  France 189 

Fig.  151  Bridge  at  Chattelerault 191,  192,  193 

Fig.  156  Bridge  at  Bilbao,  Spain 194 

Fig.  157  Cantilever  Girders 195 

Fig.  158  Arched  bridge  of  60  ft.  span 196 

Fig.  159  Arched  bridge  of  50  ft.  span 196 

Fig.  161  Foot  bridge  over  railroad,  60  ft.  span 19s 

Fig.  163  Highway  bridge  of  50  ft.  span 199 

Fig.  165  Skew  bridge  of  72  ft.  span 200 

Fig.  166  Retaining  walls  and  arched  bridge,  Paris, 

France. .'. .  .201,  202 

Fig.  168  Monier  Bridge,  Ybbs,  Austria 203 

Fig.  169  Highway  bridge  of  80  ft.  span 204 

Figs.  170-172  Reinforcing  an  old  steel  bridge  with 

concrete    ...  .200 


^«    '^    R    A    o    " 

^,  3  K  A  ft  y 
or 

UNIVERSITY 


REINFORCED  CONCRETE. 

It  can  not  be  said  that  modern  steel  structures  are 
perfection.  Prominent  engineers  foretell  great  disas- 
ters in  the  near  future  on  account  of  the  insufficient 
protection  of  the  steelwork  in  many  of  our  modern 
office  buildings.  To-day  railway  and  highway  bridges 
of  steel  are  considered  temporary  structures  and 
require  great  expense  for  maintenance.  Steel  con- 
struction is  expensive  and  not  durable.  Wood  is 
cheaper,  but  less  durable,  and  a  good  quality  of  tim- 
ber is  becoming  more  expensive  from  year  to  year. 
Owners,  architects  and  engineers  are  asking  them- 
selves what  to  do.  Shall  they  build  at  ruinous  prices 
in  steel,  or  shall  they  build  a  fire-trap  or  a  temporary 
structure?  Here  reinforced  concrete  solves  the  prob- 
lem. 

WHAT  IS  CONCRETE  AND   WHAT   IS   REINFORCED 
CONCRETE? 

Concrete  is  an  artificial  stone,  produced  by  thorough 
mixture  of  cement,  sand,  crushed  stone  or  gravel  with 
water,  placed  into  forms  and  tamped.  The  cement 
unites  chemically  with  the  water  and  binds  the  sand 
and  crushed  stone  or  gravel  so  firmly  together  that 
the  crushing  strength  of  concrete  equals  that  of  the 
most  durable  natural  stone. 

The  use  of  concrete  began  with  the  dawn  of 
civilization.  We  find  concrete  in  the  oldest  buildings 

11 


12      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

of  Mexico,  in  the  Greek  colonies  in  Italy  and  Sicily; 
the  largest  dome  in  existence,  that  of  the  Pantheon 
in  Rome,  142  feet  in  diameter,  is  a  solid  mass  of  con- 
crete, about  2,000  years  old.  In  the  Middle  Ages  we 
find  concrete  used  for  the  walls  of  many  castles  and 
abbeys. 

Concrete  fell,  eventually,  into  disuse,  during  the 
dark  Ages,  and  was  only  revived  by  the  discovery  of 
Portland  Cement  in  the  early  part  of  the  last  century, 
affording  a  much  superior  material  than  that  used 
prior  to  this  time. 

The  use  of  concrete  was  almost  entirely  confined  to 
footings  and  walls  on  account  of  its  low  tensile 
strength,  making  it  a  very  expensive  material  in  all 
cases  where  crossbending  stresses  are  to  be  overcome. 
This  deficiency  can,  however,  be  remedied  by  imbed- 
ing  steel  rods  in  the  concrete  in  proper  sizes  and  posi- 
tions, so  that  all  tensile  stresses  from  bending,  change 
of  temperature  or  initial  set  of  concrete  are  taken  care 
of. 

This  is  known  as  Reinforced  Concrete,  Concrete- 
Steel,  Ferro-Concrete  or  Armored  Concrete. 

The  first  reinforced  concrete  structure  which  came 
to  public  notice  was  exhibited  at  the  World's  Fair  in 
Paris  in  1855.  It  was  a  small  rowboat  built  by  a  Mr. 
Lamont,  of  a  shell  of  cement  mortar  11-2  inches  thick 
and  reinforced  by  a  wire  netting.  It  is  still  in  service 
in  a  pond  in  Miraval,  France. 

In  1867  MrJ  Francois  Monier  obtained  the  first  Let 
ters  Patent  on  reinforced  concrete  construction   and 
subsequently  built  many  water  tanks,   water  mains, 
sewers  and  even  houses  of  armored  concrete.     Large 
companies  are  now  doing  business  in  the  Monier  system 


RE-INFORCED  CONCRETE 


in  all  civilized  countries.  In  1877  we  find  Mr.  Thad 
deus  Hyatt  actively  engaged  in  reinforced  concrete 
construction  in  New  York  and  London.  He  built  vault- 
ings, cement  and  steel  side  walk  lights,  and  engaged 
also  in  the  fireproofing  business.  He  had  a  great  many 
tests  made  on  reinforced  concrete  beams  by  the  well 
known  Dr.  David  Kirkaldy  of  London,  which  first 
demonstrated  to  the  scientific  world  the  great  eco- 
nomical advantages  of  this  new  construction. 

During  the  last  twenty  years  Mr.  E.  L.  Ransome 
built  in  this  country  a  number  of  important  structures 
in  reinforced  concrete.  The  great  impulse  to  concrete 
construction  was  given  in  1892  when  Mr.  Francois 
Hennebique  opened  a  consulting  engineer's  office  in 
Paris,  and,  in  conjunction  with  licensed  contractors  all 
over  the  world,  designed  and  erected  nearly  ten  thou- 
sand structures  in  Armored  concrete,  valued  at  nearly 
one  hundred  million  dollars.  The  structures  designed 
by  him  were  a  success  from  the  very  beginning,  stood 
all  the  tests  prescribed  by  building  ordinances  and  spec- 
ifications of  engineers  and  architects,  and  soon  by  their 
great  strength  and  durability  and  their  low  price  found 
favor  with  municipal  and  state  governments,  who,  after 
careful  investigation,  adopted  them  for  work  of  the 
greatest  importance. 

We  will  now  explain  the  various  details  of  armored 
concrete  construction  classified  as  follows:  Girders, 
floor  slabs,  roofs,  columns,  walls,  retaining  walls,  tanks, 
stairs,  etc. 


THE  ARMORED  CONCRETE  GIRDER. 

Fig.  i  shows  the  elevation,  Fig.  2  the  section,  Fig. 
3  a  perspective  view  of  the  girder.  It  consists  essen- 
tially of  a  concrete  rib  reinforced  by  plain  round  steel 
rods,  part  of  which  are  straight  and  part  of  which  are 
bent  into  hog  chain  form,  and  a  number  of  "U"  bars 
or  stirrups  of  hoop  steel.  In  comparison  with  a  steel 
girder  (see  Fig.  2)  we  see  that  the  lower  flange  of 
the  steel  girder  is  replaced  by  the  steel  rods,  the  upper 
flange  of  the  steel  girder  by  the  concrete  floor  and  the 
web  by  the  concrete  rib  and  the  "U"  bars. 

The  reader  will  ask  the  reason  for  bending  up  the 
steel  rods  and  for  the  "U"  bars.  Experience  has  dem- 
onstrated that  concrete  ribs,  which  are  reinforced  by 
a  high  percentage  of  steel,  which  is  nearly  always  the 
case,  the  girders  being  made  as  small  as  possible  to 
save  head-room,  weight  and  forms,  do  not  show  the 
first  signs  of  failure  in  the  center,  but  show  it  near 
the  supports  by  diagonal  cracks,  produced  by  the  com- 
bined shearing  and  tensile  stresses  which  are  maximum 
near  the  supports.  The  inclined  portion  of  the  bent 
rods  take  up  part  of  the  shear  and  the  "U"  bars,  which 
are  set  close  together  near  the  supports,  take  up  the 
tensile  stresses  which  arise  from  the  action  of  the 
remaining  part  of  the  shear. 

A  reinforced  concrete  girder  is  much  safer  with  "U" 
bars  than  without  them.  Should  the  concrete  ribs  from 
any  reason  crack  vertically  or  diagonally,  it  is  clear 

14 


RE-INFORCED  CONCRETE  GIRDERS 


& 


& 


16      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

that  the  steel  rods  would  alone  hold  the  girder  together 
and  that  there  would  be  a  tendency  to  push  the  rods 
out  of  the  concrete,  which  cannot  happen  where  the 
"U"  bars  are  used. 

We  have  said  that  the  concrete  floor  takes  up  the 
compression  of  a  concrete-steel  girder,  and  in  most 
cases  the  section  of  the  concrete  floor  suffices;  in  case 


Fig.  3. — Perspective  View  of  Armored  Concrete  Girder. 


of  heavy  girders  of  small  depth,  however,  also  the 
top  part  of  the  concrete  rib  is  to  be  reinforced  by  steel 
rods,  which  must  take  up  the  difference  between  the 
figured  compression  in  the  upper  part  of  the  girder  and 
the  compression,  which  it  is  safe  to  allow  on  the  con- 
crete floor. 

In  building  construction  girders  are  seldom  freelv 
supported  at  the  ends.  They  are  monolithically  con 
nected  with  other  girders,  they  are  continuous,  and 
therefore  much  stronger  than  freely  supported  girders. 
The  deflection  of  the  girders  is  considerably  reduced, 
as  we  know  that  continuous  girders  show  deflections, 
which  are  one- half  to  one-fifth  the  deflection  of  freely 
supported  girders. 


RE-INFORCED  CONCRETE  GIRDERS 


17 


Fig.  4.  —  Connection  of  a  Continuous  Girder  to  a  Column. 


The  economical  depth  of,  armored  concrete  girders 
about  equals  the  depth  of  steel  girders  of  the  same 
carrying  capacity  and  should  not,  as  a  general  rule,  be 
less  than  1-20  of  the  span.  The  width  of  these  girders 
is  : 

6  inches  for  girders  corresponding  to  12  inch  I  beams. 
8  inches  for  girders  corresponding  to  12  inch  to  18  inch 

I  beams. 
10  inches  for  girders  corresponding  to  20  inch  to  24 

inch  I  beams. 
12  inches  for  girders  corresponding  to  rivetted  girders 

of  30  to  40  inches  height. 
Up  to  24  inches  for  girders  corresponding  to  very 

heavy  box  girders. 


Fig.  5. — Forms  for  Girders  and  Floors. 


18      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Concrete  girders  are  manufactured  in  wooden  molds, 
called  forms,  at  the  site,  in  place,  where  they  belong, 
as  shown  in  Fig.  5.  The  mold  for  each  beam  consists 
of  a  2  inch  bottom  plate,  and  two  2  inch  side  plates, 
screwed  or  clamped  to  the  bottom  piece.  These  molds 
should  be  supported  every  five  feet  by  an  upright,  and 
the  striking  of  the  centering  for  the  girders  should 
not  be  commenced  before  three  or  four  weeks  after 
concreting.  j 


Fig.  6.— This  Beam  was  designed  for  a  super-imposed  load 
of  4  tons,  and  was  tested  by  a  load  of  34  tons.  It 
cracked  in  the  center  and  deflected  considerably;  nev- 
ertheless, it  carried  the  load  for  4  years  without  further 
sign  of  weakness. 

Reinforced  concrete  girders  can  span  any  distance 
used  in  building  construction,  and  carry  any  load  up 


RE-INFORCED  CONCRETE  GIRDERS  19 

to  many  hundred  tons.  In  the  larger  spans  the 
weight  becomes  excessive  and  we  can  lay  down  a  limit 
for  -the  span  of  these  girders  in  buildings  at  perhaps 
100  ft.,  for  bridges  perhaps  150  feet;  arched  ribs,  how- 
ever, can  be  built  for  much  larger  spans. 

We  see  thus,  that  the  science  of  reinforced  concrete 
girders  is  well  developed;  all  stresses  as  tension,  com- 
pression, and  shear,  are  properly  cared  for  by  the  ex- 
perienced designer,  and  the  result  is  an  indestructible 
girder  construction,  which  under  tests  proves  a  strength 
beyond  expectation.  We  cite  the  following  tests  made 
on  girders  designed  In  Armored  Concrete  which 
tests  were  made  according  to  contracts  when  the  build- 
ings were  partly  or  wholly  completed,  and  which  tests 
must  convince  any  fair-minded  person  of  the  safety  o[ 
this  modern  construction,  which  is  destined  in  the  near 
future,  to  be  the  only  construction. 

Mr.  Frederick  Baird,  Architect,  218  American  Trust 
Bldg.,  Cleveland,  O.,  writes: 
MR.  L.  J.  MENSCH, 

Monon  Building,  Chicago, 

DEAR  SIR  :  Regarding  the  test  made  at  the  Salva- 
tion Army  building,  Dec.  16,  1902,  I  am  pleased  to 
give  you  the  following  data :  The  floor  beams  tested 
were  8  ins.  x  16  ins.,  7  ft.-o  o.  c.,  with  clear  span  of 
23  ft.  6  ins.  One  end  of  same  connects  to  a  column, 
and  the  other  to  a  girder  8  ins.  x  16  ins.  near  the  center 
of  the  same.  The  girders,  floors,  columns,  footings, 
galleries  and  stairs  were  all  constructed  in  ar- 
mored concrete,  to  sustain  a  live  load  of  125  Ibs.  per 
sq.  ft.  floor  loads.  In  the  test,  the  above  floor  space 
over  the  girder  7  ft.  x  23  ft.  was  loaded  gradually  to 
600  Ibs.  per  sq.  ft,  which  was  approximately  100,000 


20      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Ibs.  on  the  beam.     The  greatest  deflection  was  about 
3-8  in.,  and  the  final  set  was  1-8  in. 

The  beams  and  floors  showed  no  signs  of  cracks  or 
other  defects,  and  the  whole  test  was  eminently  satis- 
factory. The  construction  throughout  and  the  materi- 
als used  were  of  the  best  quality,  and  promise  to  be 


Fig.   7.— Test  of   Girder,    Salvation    Army    Building,     Cleve- 
land,  O. 

as   durable  as  anything  yet  obtainable  or  known  to 
science — and  also  caused  us  a  saving  of  23  per  cent 
over  the  cost  in  steel  framing  with  tile  floors. 
Yours  truly, 

(Signed)  FREDERICK  BAIRD. 


RE-INFORCED  CONCRETE  GIRDERS 


/.  Sec  /to  /» 


Fig.  8. — Diagram  of  Girder  24  feet,  Ginches  span,  loaded 
with  100,000  pounds,  Salvation  Army  Building,  Cleve- 
land. 


22      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Mr.  F.  B.  Heathman,  Architect,  Dayton,  O.,  writes ; 
MR.  L.  J.  MENSCH, 

Monon,  Bldg.,  Chicago,  Illinois. 

DEAR  SIR  :     In  answer  to  your  letter  inquiring  about 
the  tests  made  on  the  concrete  floors  and  girders  at 


Fig.  9. — Test  of  Girder  of  27  feet  span  at  the  Davis  Sewing 
Machine  Company's  Office  and  Ware-house.  Load, 
124,000  pounds. 

the  Davis  Sewing  Machine  Co.,  of  this  city,  I  ant 
pleased  to  say  that  they  were  more  than  satisfactory, 
and  that  the  company  and  all  concerned  are  praising 
the  work. 


RE-INFORCED  CONCRETE  GIRDERS       «       23 

The  long  girders,  26  ft.  span,  were  the  only  ones 
tested.  The  floor  was  weighted  to  400  pounds  per 
square  foot,  twice  the  load  for  which  is  was  designed. 


Fig.  10. — Concreting  of  Floors,  Davis  Sewing  Machine  Co. 

making  124,800  pounds  on  one  girder.     The  greatest 
deflection  was  found  to  be  only  one-tenth  of  an  inch. 
Very  truly  yours, 

(Signed)  F.  B.  HEATHMAN. 

Mr.  G.  W.  Drach,  Architect,  Cincinnati,  O.,  writes . 
MR.  L.  J.  MENSCH, 

Monon  Building,  Chicago, 

MY  DEAR  MR.  MENSCH  :     The  test  of  the  balcony  at 
the  College  of  Music  was  very  satisfactory.    The  bal- 


24      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  GIRDERS  2o 

cony,  with  girders  of  61  foot  span,  was.  loaded  in  the 
in  the  center  a  little  over  51,000  pounds.  The  deflec- 
tion was  3-16  of  an  inch.  We  propose  to  allow  the  load 
to  remain  until  to-morrow.  The  deflection  has  not  in- 


Fig.  11. — Balcony  Girders  of  61  feet  span,  College  of  Music. 
Cincinnati,  O.,  One  girder  2  feet  8  inches  deep,  one 
Girder  3  feet  2  inches  deep. 

creased  any  from  4  o'clock  p.  m.  yesterday  up  to  9 
o'clock  this  morning. 

Yours  very  sincerely, 

(Signed)  GUSTAVE  W.  DRACH. 
Mr.  Paul  S.  Ward,  Mech.  Engineer  for  the  J.  H. 
Day  Co.,  Harrison  and  Bogen  Aves.,  Cincinnati  writes  : 
MR.  L.  J.  MENSCH, 

Chicago,  111. 

DEAR  SIR  :     Yours  of  September  3rd  at  hand  asking 
us  for  report  of  test  of  concrete  floor  in  our  new  foun- 


26      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

dry  building^  and  are  sending  you  herewith  a  brief 
statement  of  the  result  of  the  test  as  made  on  the  sec- 
tion of  the  building  adjacent  to  the  old  shop. 


Fig.  13. — Test  load  of  77  000  pounds,  J.  H.  Day  &  Co.'s  Foun 
dry,  Cincinnati,  O. 

We  first  tested  a  floor  beam  in  the  construction, 
loaded  it  with  a  uniform  distributed  load  over  a  sur- 
face of  10x20  feet.  The  beam  being  immediately 
under  the  longitudinal  center  line  of  this  surface,  and 
as  the  contract  required  this  to  sustain  a  load  of  375 
pounds  per  sq.  ft.  with  a  deflection  not:  to  exceed  1-800 
of  the  length  of  the  span,  we  distributed  77,000  pounds 
of  pig  iron  as  uniformly  as  practicable  over  the  sur- 
face mentioned  above.  The  beam  showed  a  deflection 
of  1-16  of  an  inch  when  1-3  of  the  load  had  been 


RE-INFORCED  CONCRETE  GIRDERS  2? 

placed,  but  this  only  increased  to  2.4.  MM,  or  about 
3-32  of  an  inch  with  the  full  load  of  77,000  pounds 
with  no  evidence  of  any  weakness,  no  cracks  develop- 
ing, or  none  showing  that  might  have  existed  before 
the  load  was  placed. 

We  next  loaded  a  girder  with  as  nearly  a  concen 
trated  load  as  was  possible,  if  you  will  remember  the 


Fig.  14. — Lintel  of  33  feet  span,  supporting  a  wall  60  feet 
high  with  several  floors.  J.  H.  Day  &  Co.'s  Foundry, 
Cincinnati,  O. 

sections  in  this  construction  were  20  feet  centers 
and  square.  We  placed  therefore  on  this  girder  77,000 
pounds,  on  a  base  as  small  as  was  practicable,  with  the 
object  of  approximating  a  concentrated  load,  and  as 
before  found  that  the  girder  showed  above  75  per  cent 


28      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

of  its  ultimate  deflection  with  about  1-3  to  1-2  load.  The 
whole  load  of  77,000  rested  on  a  span  6  feet  square 
Under  the  entire  load,  the  beam  showed  a  maximum 
deflection  of  2.6  MM,  with  no  evidence  of  any  greater 
deflection  after  the  load  had  remained  72  hours. 


Fig.    15. — Floor   of   20  ft.    span,   and    Columns   26   feet   high. 
J.  H.  Day  &  Co.,  Cincinnati, 

Lastly,  we  selected  the  largest  floor  panel  in  the 
construction,  viz. :  one  12  feet  wide  by  19  1-2  feet  long, 
and  we  loaded  this  with  38,000  pounds  of  pig  iron  on 
a  base  4  feet  wide  by  19  1-2  feet  long  over  the  middle 
of  the  span.  This  load  on  a  ^375  pound  basis  should  be 
about  43,000  pounds,  however,  after  the  placing  of  the 
load  the  deflection  at  the  middle  of  the  span  was  1-8 
of  an  inch. 


RE-INFORCED  CONCRETE  GIRDERS' 


30      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Hoping  this  report  is  satisfactory,  we  are, 
Yours  very  truly, 

THE  J.  H.  DAY  COMPANY, 
(Signed)  PAUL  S.  WARD, 

Mech.  Engr. 

Messrs.  Dittoe  &  Wisenall,  Architects,  Cincinnati 
O.,  write: 
MR.  L.  J.  MENSCH, 

Chicago,  111. 

DEAR  SIR  :  On  May  20,  1903,  we  witnessed  a  test 
made  on  armored  concrete  girders  and  floor  construc- 
tion of  the  Hennebique  system  in  the  new  warehouse 
for  the  Champion  Ice  Co.,  Covington,  Ky.,  and  which 
work  was  installed  by  you  under  our  direction. 

The  girders  were  located  7  ft.  6  ins.  apart,  of  18 
feet  span  and  were  figured  for  a  superimposed  floor 
load  of  250  pounds  per  square  foot.  A  floor  area  of 
14x18  feet  was  loaded  with  100,000  pounds,  i.  e.,  400 
pounds  per  square  foot,  and  the  maximum  deflection 
reached  i-io  of  an  inch.  These  girders  were  supported 
by  10  inch  columns  and  4  inch  concrete  partitions  and 
as  the  owners  of  the  building  were  afraid  of  the  column 
and  partition  construction,  the  100,000  pound  load  was 
left  upon  the  second  floor  and  directly  above  the  same, 
on  the  third  floor,  an  area  of  14x18  feet  was  loaded 
with  150,000  pounds,  equal  to  600  pounds  per  square 
foot,  and  the  greatest  deflection  reached  was  1-8  of  an 
inch,  and  not  the  least  sign  of  cracks  or  weakness  in 
the  columns  or  partition  work  could  be  discovered 
although  both  of  these  loads  were  allowed  to  remain 
in  place  for  several  days  and  upon  the  removal  of  the 
same,  the  floors  and  girders  resumed  their  normal  po- 
sition. 


RE-INFORCED  CONCRETE  GIRDERS  31 

We  were  very  much  gratified  with  the  success  of 
this  test.  The  building  has  now  been  loaded  for  sev- 
eral months  to  its  safe  capacity  with  goods  which  were 
kept  in  cold  storage  during  this  season  of  the  year,  and 
the  building  is  very  satisfactory  for  this  purpose. 


Fig.  17. — Test  of  Girders  and  Floor.  Champion  Ice  Co.'s  Cold 
Storage  House,  Covington,  Ky.  Load,  150,000  pounds; 
400  pounds  per  square  foot. 

We  believe  this  material  and  your  system  to  be  an 
excellent  building  material  for  buildings  of  this  class 
and  we  wish  you  the  success  which  your  knowledge 
of  its  use  certainly  deserves. 

-  Yours  respectfully, 
(Signed)  DITTOE  &  WISENALL, 

Architects 


32      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig<  18._Test  of  Girders  and  Floor.  Champion  Ice  Co.'s  Cold 
Storage  House,  Covington,  Ky.  Load,  150,000  pounds; 
603  pounds  per  square  foot. 

Fig.  19  shows  a  test  of  girders  of  the  library  floor 
of  the  new  McKinley  High  School,  Russell  and  Ann 
Aves.,  St.  Louis,  Mo.,  Wm.  B.  Ittner,  Architect. 

The  girders  tested  spanned  32  feet.  The  entire  floor 
of  32x36  feet  was  uniformly  loaded  with  264,000  Ibs 
representing  a  load  of  220  Ibs.  per  square  foot,  that 
is,  three  times  the  figured  load. 

The  deflections1  in  the  center  of  the  beams  were : 

At  a  load  of  105  Ibs.  per  square  foot 0.087  inches 

At  a  load  of  160  Ibs.  per  square  foot 0.165  inches 

At  a  load  of  220  Ibs.  per  square  foot 0.323  inches 


RE-INFORCED  CONCRETE  GIRDERS 


33 


Under  three  times  the  load  the  deflection  was  i-i  190 
of  the  span;  after  removal  of  the  load,  there  remained 
a  permanent  deflection  of  0.118  inches. 


Flg>  19._ Test  load,  Library  floor,  McKinley  High  School 
St.  Louis,  Load,  264,000  pounds;  220  pounds  per  square 
foot. 

We  also  refer  to  another  very  convincing  test  made 
on  girders  of  fifty-seven  feet  span  at  the  new  Lyric 
Theatre,  Cleveland,  Ohio.  These  girders  were  figured 
to  carry  an  uniformly  distributed  load  from  the  bal- 
cony of  65,000  pounds,  and  were  tested  by  hanging  a 
load  of  pig  iron  of  88,000  pounds  from  the  center. 


34      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


frill 


which  is  equivalent  to  a  distributed  load  of  176,000 
pounds.  The  greatest  deflection  was  9-16  of  an  inch 
and  the  permenant  deflection  was  less  than  1-8  inch. 


CONSTRUCTION     OF     REINFORCED     CON- 
CRETE FLOORS. 

The  floor  slabs  connecting  the  beams  or  walls  are 
generally  from  2  1-2  to  6  inches  thick  and  reinforced 
by  1-4  to  3-4  inch  steel  rods  3  to  12  inches  on  centers. 

These  slabs  are  usually  continuous,  therefore,  tensile 
stresses  are  set  up  not  only  at  the  underside  of  the  slab 
in  the  center  of  the  span,  but  also  over  the  supports  in 
the  top  fibres,  and  the  steel  rods  have  to  be  bent  in  hog 
chain  form,  as  shown  in  Figures  2  and  21,  to  take 
care  of  these  tensile  stresses.  Sometimes  it  is  even 
necessary  to  imbed  short  extra  rods  in  the  upper  part 
of  the  slab. 

For  any  given  percentage  of  steel  reinforcement, 
the  carrying  capacity  of  the  slabs  is  proportional  to 
the  square  of  the  height. 

The  following  table  gives  the  maximum  live  loads 
per  square  foot,  which  these  slabs  are  able  to  carry 
with  a  factor  of  safety  of  four  or  five,  when'  reinforced 
by  a  very  high  percentage  of  steel. 


Thickness 

of  slab 

Span  in  feet. 

in  inches. 

Si  ^ 

7 

8j  9|  10 

12 

14 

16 

18 

3 

450 

300 

200 

140 

3/ 

600 

400 

280 

200 

140 

4 

560 

390 

280 

200 

160 

90 

4/2 

690 

500 

370 

270 

210 

I30 

70 

5 

640 

470 

360 

270 

170 

IOO 

60 

6 

690 

530 

410 

260 

1  60 

IOO 

60 

35 


36      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

It  is  always  more  economical  to  use,  a  greater  depth 
than  those  given  in  the  table;  this  reduces  the  amount 
of  steel  required  and  cheapens  the  cost  of  the  floor. 

It  is  advisable  to  use  these  slabs  for  spans  not  ex 
ceeding  8  feet  for  heavy  load,  say  200  Ibs.  per  square 


T 


ts/ee/>Ws 


LH 


Fig.  21. — Girder,  Beam  and  Slab  Construction. 


foot  and  over,  and  for  spans  not  exceeding  12  feet  for 
lighter  loads,  and  adopt,  where  economy  is  the  prin- 
ciple consideration,  an  arrangement  of  beams,  girders 
and  floor  slabs  as  shown  in  Fig.  21. 


RE-INFORCED   CONCRETE   FLOORS 


37 


Much  greater  spans  can  be  adopted,  when  the  floor 
slabs  are  nearly  square  and  supported  on  all  four  sides 
as  shown  in  Fig.  22. 


* 

— u_ 


n 


Fig.  22. — Girder  and  Square  Slab  Construction. 

In  this  case  the  slabs  are  reinforced  by  steel  rods-in 
both  directions,  and  the  supporting  girders  have  to 
carry  orify  one  quarter  of  the  load  of  each  panel,  anc 
as  two  panels  usually  meet  over  the  beams,  they  have  to 
be  figured  for  half  of  the  panel  load,  which  loading  is 
about  a  mean  between  a  concentrated  and  a  distrib- 
uted load. 


38      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

The  following  table  gives  the  maximum  live  loads 
that  nearly  square  slabs,  reinforced  by  a  very  high  per- 
centage of  steel  in  both  directions,  will  carry  with  a 
factor  of  safety  of  four  to  five : 


Thickness 
of  slab 
in  inches. 

Side  of  square,  in  feet. 

6|      8 

io|    12!    14 

1                  | 

16 

18 

20 

25 

3 
4 

4/2 

5 
6 

800 

400 
600 

250 
350 
550 
800 

230 
360 
480 
700 

150 
250 
360 
480 
730 

1  80 

250 

350 
540 

190 

250 
400 

300 

Here  also  it  is  more  economical  to  use  greater  depth 
than  given  in  the  table. 

This  arrangement  of  square  or  nearly  square  slabs 
lends  itself  easily  to  decoration,  and  is  no  more  ex- 
pensive for  light  loads,  and  very  little  more  for  heavier 
loads,  than  the  ordinary  slab  and  beam  construction, 
and  is  a  very  appropriate  arrangement  for  public  build 
ings,  department  stores,  etc. 


r 


Fig.  23. — Section  Through  Hollow  Concrete  Floor. 

Where  flat  ceilings  for  spans  of  more  than  18  feet 
are  required,  a  hollow  floor  construction,  as  shown  in 
Fig.  23,  gives  very  satisfactory  results. 


RE-INFORCED   CONCRETE  FLOORS 


39 


*  "P    J 


Fig.  24. — Test  of  Hollow  Floors,  Sheldon  residence,  New  York 

City. 


40      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

This  floor  consists  of  ribs  4  inches  to  6  inches  thick 
and  about  three  feet  apart,  which  are  reinforced  by 
straight  and  bent  bars  and  stirrups,  a  i  1-2  inch  ceiling, 
strengthened  by  light  steel  rods  in  both  directions  and 
a  2  1-2  to  4  inch  reinforced  concrete  floor.  The  depth 
of  these  floors  is  10  inches  for  18  feet  spans,  and  20 
to  24  inches  for  40  feet  spans. 

Fig.  24  shows  the  diagram  of  a  test  load  on  such 
floors  of  22  feet  span,  at  the  Sheldon  House,  38  E. 
40th  Street,  New  York  City,  in  presence  of  the  repre- 
sentative of  Mr.  Ernest  Flagg,  the  architect,  and 
engineers  of  the  New  York  Building  Department. 
The  floor  was  tested  to  350  Ibs.  per  square  foot,  and 
the  greatest  deflection  was  1-25  of  an  inch. 


1 

0| 

• 

-    '  "  -    '  4'v-  .^ 

1  '      1  TTjTl  ' 

IT 

3               1      it                  /***$ 

r^y-^v^vfe;^Eid=a;Ej 

TT^ 

.0.30. 


Fig.  25. — Section  Through  Girder  and  Floor  Construction  with 
Reinforced  Concrete  Ceiling. 

The  ceiling  and  the  ribs  are  usually  concreted  first 
and  the  centering  for  the  floor  is  obtained  by  wire  net- 
ting, or  arched  match  boards,  or  thin  concrete  plates, 


RE-INFORCED   CONCRETE  FLOORS 


41 


®   o 

fl 


42      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


il 

li 

J3     P 


o  ' 

8  M 

^  CO 

P'  CT 

I  "I 

o 


RE-INFORCED   CONCRETE   FLOORS 


L3 


Fig.   28. — Electric   Fountain   and   Cascade,   Paris   Exposition. 
1900.     The  most  elaborate   structure  of  armored   con 
crete  ever  erected.    140  feet  high. 


44      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

etc.  These  hollow  floors  are  of  great  advantage  in 
cold  storage  houses,  as  a  less  conductive  floor  constfuc- 
tion  can  hardly  be  imagined. 

The  centering  for  floor  slabs  may  be  removed  eight 
days  after  concreting,  if  the  weather  was  moderate 
during  this  time;  but  when  the  temperature  has  been 
near  the  freezing  point  it  is  advisable  to  wait  14  days 
with  the  striking  of  the  forms.  Most  of  the  accidents 
which  happen  in  concrete  construction  are  due  to  the 
fact  that  the  centering  was  removed  before  the  concrete 
had  sufficiently  hardened. 


Fig.  29.— Front  View  of  the  Same. 

In  warm  and  dry  weather,  the  upper  layer  of  the 
concrete  slabs  sets  up  very  quickly  while  the  interior 
remains  soft,  resulting  in  fine  cracks  in  the  surface. 
To  prevent  this,  the  floors  must  be  sprinkled,  at  least 


RE-INFORCED   CONCRETE  FLOORS  45 

every  two  hours,  for  a  few  days  after  concreting.  These 
cracks  appear  very  soon  where  the  floors  are  exposed 
to  the  direct  rays  of  the  sun.     This*  must  be  guarded 
against  by  covering  the  concrete  with  cloth  and  sprink 
ling  it  very  often  with  water. 

Frost  retards  the  setting  of  the  concrete.  The  water 
freezes  and  the  cement  cannot  enter  into  the  chemical 
union  with  the  water.  Frozen  concrete  will  be  found 
green  in  the  inside  after  months  of  exposure;  the 
cement  has  not  been  destroyed,  however.  If  the  con- 
crete is  sprinkled  with  water;  once  the  temperature 
is  again  above  freezing,  the  water  will  soak  into  the 
concrete,  and  the  cement  continue  to  set.  This 
sprinkling  should  be  continued  for  at  least  a  week. 
Repeated  freezing  and  thawing  will  usually  destroy 
concrete,  which  is  not  more  than  14  days  old.  The 
water  by  freezing  expands  and  ruptures  the  concrete. 
Therefore,  if  concreting  has  to  be  carried  on  in  weather 
near  the  freezing  point,  all  exposed  surfaces  should  be 
covered  with  cloth  and  a  layer  of  sand. 

FINISH    OF    CONCRETE    FLOORS. 

The  most  common  method  of  finishing  concrete 
floors  is  by  laying  bevelled  2  in.  x  2  in.  sleepers,  16  in. 
centers,  on  the  concrete  floor,  and  by  weighing  down 
these  sleepers  by  a  i  1-2  inch  layer  of  cinder  con- 
crete and  nailing  the  wood  floor  on  the  sleepers  as 
shown  in  Fig.  30. 


Fig.  30. — Wood  Floor  on  Concrete  Slab. 


46      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

We  secure  a  half  inch  air  space,  which  makes  the 
floor  much  more  sound  and  heat  proof. 

The  cinder  concrete  should  be  mixed  in  the  propor- 
tion of  3-4  barrel  of  Portland  cement  (though  one 
barrel  of  Hydraulic  cement  also  gives  good  results; 
to  one  yard  of  cinders  with  a  moderate  amount  of 
water.  If  too  much  water  be  used  the  sleepers  will 
absorb  the  water  and  warp.  Careful  builders  usually 
hold  up  the  sleepers  by  planks  and  uprights  against  the 
ceiling  to  insure  a  good  job. 

For  factories,  storage  houses,  etc.,  the  concrete  floors 
are  generally  finished  by  a  half  to  3-4  inch  coat  ot 
cement  mortar,  cement  and  sand  being  mixed  in  the 
proportion  of  one  to  two.  This  wearing  surface  should 
be  spread  on  the  concrete  while  the  latter  is  still  soft 
and  adhesive.  If  this  cannot  be  done  at  this  time,  the 
surface  of  the  concrete  should  be  scraped  and 
thoroughly  cleaned  and  well  sprinkled  with  water  and 
afterwards  with  neat  cement  before  the  finishing  coat 
is  applied. 

Granitoid  finish  is  used  for  corridors  of  public  build- 
ings, and  is  a  wearing  surface,  generally  one  inch 
thick,  composed  of  one  part  Portland  cement  to  i  1-2 
parts  of  crushed  granite,  in  size  from  3-8  inch  down. 

Cracks  in  the  cement  finish  are  prevented  by  divid- 
ing the  wearing  surface  along  the  main  girders. 

Hotels  and  apartment  buildings  where  the  floors 
are  covered  by  heavy  carpets  need  no  other  finish 
whatever,  only  special  care  has  to  be  taken  to  have 
the  surface  of  the  concrete  floor  fairly  smooth.  In  this 
case  nailing  strips  can  be  imbedded  in  the  concrete  to 
fasten  the  carpets,  and  eventually  some  finish  provided 
on  the  sides  of  the  rooms  or  corridors  for  a  margin. 


RE-INFORCED   CONCRETE  FLOORS 


48      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Lime  plaster  adheres  firmly  to  concrete  work  and  the 
illustrations  show  some  highly  ornamental  plaster  work 
in  this  line. 

RE-INFORCED    CONCRETE    ROOFS. 

The  roof  construction  is  similar  to  that  of  floors 
only  that  the  construction  is  generally  much  lighter. 
It  is,  however,  not  advisable  to  reduce  the  thickness 
of  the  floor  slabs  below  31-2  inches  to  avoid  cracking. 


Fig.    32.*— All-concrete    Foundry,    Hull,    England.    Unusually 
well  lighted.    Span  of  girders,  40  feet. 

Roofs  are  exposed  to  great  and  often  sudden  changes 
of  temperature  and  must  be  guarded  against  cracking 
by  imbedding  plenty  of  steel  rods  in  both  directions 
in  the  slabs. 

Concrete  roofs  are  not  water  proof  by  themselves. 
They  must  have  a  water  proof  covering.     A  reliabL 


RE-INFORCED   CONCRETE   FLOORS  49 

and  inexpensive  covering  is  a  tar  and  gravel  roof 
which  can  be  laid  directly  on  the  concrete  surface  of 
the  roof,  without  any  intermediate  wood  floor.  A  more 
expensive  covering,  yet  a  very  durable  one,  is  a  one 
:nch  layer  of  asphalt. 

Another  method,  which  is,  however,  not  to  be  rec- 
ommended, is  by  spreading  a  one  inch  coat  of  cement  * 
mortar,  composed  of  i  part  cement  and  11-2  parts  of 
sand  on  the  concrete.     Only  very  experienced  work- 
men can  c1o  a  good  job,  and  it  is  safer  first  to  paint 
the  surface  of  the  concrete  floor,  with  a  water  proof 
asphalt  paint,  for  example,  Toch  Bros.'  R.  I.  W.  painty 
and  spreading  on  the  thus  prepared  surface,  the  cement 
finish. 

The  cement  coat  preserves  the  asphalt  paint  which 
soaks  into  the  concrete,  and  adheres  to  it  with  great 
force,  and  makes  it  water  proof,  and  should  the  cement 
finish  crack,  the  water,  which  may  come  through  the 
crack,  cannot  soak  into  the  concrete  of  the  roof. 

The  lowest  layer  of  the  roof  slabs  should  be  made  of 
a  rather  porous  concrete  in  order  to  absorb  the  moisture 
which  arises  there  from  condensation,  thus  preventing 
drops  falling  from  the  ceiling. 

Concrete  roofs  built  in  Cleveland,  Cincinnati,  and 
other  places,  gave  no  cause  of  complaint  in  this 
direction. 

WEIGHT  OF  CONCRETE  FLOORS. 

The  weight  of  one  square  foot  of  concrete  one  inch 
thick  is  12  Ibs.  Therefore,  the  weight  of  a  concrete 
floor  per  square  foot  is  found  by  multiplying  the  thick- 
ness of  the  concrete  in  inches  by  12  and  adding  15  Ibs. 
for  sleepers,  cinder  concrete,  wood  floors  and  plaster- 
ing. 


50      RE-INFORCED  CONCRETE  CONSTRUCTIONS 
FLOOR    LOADS. 

Very  careful  consideration  of  the  floor  loads  to  be 
specified  for  a  building  will  often  save  a  considerable 
amount  of  expense.  Floors  for  residences  do  not  re- 
quire to  be  figured  for  more  than  forty  pounds  per 


Fig.  33. — Foundry  Building  of  Armored  Concrete  Construc- 
tion. The  columns  support  a  track  for  a  30  ton  travel- 
ing Crane.  Note  holes  in  columns  for  attaching  bear- 
ings of  radial  drilling  machines. 

square  foot.  Experiments  made  in  Boston  demon- 
strate that  the  live  loads  in  office  buildings  are  rarely 
more  than  fifty  pounds  per  square  foot  and  do  not 
generally  exceed  more  than  ten  pounds.  Therefore,  it 
will  be  good  practice  to  figure  the  floor  slabs  for  60 
Ibs.  per  square  foot;  this  will  allow  a  good  margin 


RE-INFORCED   CONCRETE   FLOORS  51 

lor  heavy  safes  or  similar  loads.  A  reduction  of  floor 
loads  can  be  made  for  the  girders  and  a  still  greater 
reduction  for  the  columns — as  experience  has  repeat- 
edly demonstrated  that  floor  loads  vary  only  from  10 
to  50  pounds.  School  buildings  do  not  require  to  be 
figured  for  more  than  fifty  to  sixty  pounds  per  square 
foot. 

Department  stores,  warehouses,  and  factories  have 
floor*  loads  which  vary  considerably.  It  is  to  be  borne  in 
mind,  however,  that  in  all  these  case3  only  a  small 
part  of  the  floor  area  is  really  loaded  with  the  heaviest 
class  of  goods  or  machinery,  and  that  there  are  usually 
many  aisles  and  cross  aisles  taking  up  as  much  as 
twenty  to  fifty  per  cent,  of  the  floor  area. 

If,  for  example,  a  live  load  of  150  pounds  per  square 
foot  is  specified,  it  means  that  all  columns,  girders, 
beams  and  slabs  have  to  be  figured  for  a  load  which  is 
equal  to  the  area  carried  by  these  members  multiplied 
by  150.  Very  often  this  load  of  150  pounds  is  speci- 
fied for  very  light  manufacturing  purposes,  which  is 
only  a  waste  of  money,  as  in  a  panel  14  feet  square,  for 
example,  there  will  probably  never  be  anything  near  to 
30,000  pounds  which  this  specification  would  require. 

The  writer  determined  the  live  loads  in  one  of  the 
heaviest  hardware  houses  in  Cleveland,  Ohio,  and 
found  that  the  average  load  on  the  top  floor  was  not 
more  than  forty  to  fifty  pounds  per  square  foot;  and 
on  another  floor  loaded  with  enamel  ware,  scales, 
shovels  in  bundles  of  twelve  pieces,  which  materials 
weigh  about  150  pounds  per  square  foot,  the  average 
load  was  not  more  than  100  pounds. 

Floors  loaded  with  axes,  picks,  barrels  of  hinges 
and  barrels  of  tacks,  weighing  about  500  pounds  per 


52      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

square  foot  had  an  average  distributed  floor  load  of  not 
more  than  250  to  300  pounds.  The  ground  floor, 
loaded  with  butts,  tin  plates,  sixteen  boxes  high,  gas 
pipes,  etc.,  weighing  900  pounds  per  square  foot,  had 
an  average  floor  load  of  500  to  600  pounds.. 


Fig.  34. — >Armored  Concrete  Columns. 


CONSTRUCTION     OF     REINFORCED     CON- 
CRETE COLUMNS. 

Concrete  columns  are  reinforced  by  4,  6,  8,  up  to  20 
or  more  steel  rods  in  diameters  from  3-8  inch  to  2  1-2 
inches.  As  seen  in  Fig.  34,  the  rods  are  placed  near 
the  circumference,  give  therefore  the  largest  radius  of 
gyration,  and  are  in  a  position  to  take  up  tensile 
stresses,  which  may  be  produced  by  excentric  loading, 
wind  pressure,  pull  of  beltings,  or  lateral  shocks.  The 
strength  of  these  columns  is  the  sum  of  the  strength  of 
the  concrete  plus  the  strength  of  the  steel  rods,  and  as 
the  concrete  is  here  more  carefully  rammed  than  in 
other  concrete  work,  we  can  safely  allow  300  to  400 
Ibs.  per  square  inch  in  the  concrete.  The  stress  in 
the  steel  rods  may  be  computed  by  the  same  rule  as  for 
ordinary  steel  columns.  These  columns  fail  mostly  by 
the  shearing  of  the  concrete  under  45  degrees,  (see 
Fig-  35)  and  by  pushing  the  steel  rods  apart,  there- 
fore, we  have  to  connect  the  different  steel  rods  by  ties 
in  intervals  of  not  more  than  the  diameter  of  the 
column.  The  following  table  gives  the  maximum  loads 
which  square  columns,  not  exceeding  in  height  1 5  times 
the  diameter,  will  carry  with  a  factor  of  safety  of  four 
to  five : 


Side  of 
square  in 
inches 

8 

10 

12 

14 

16 

18 

20 

22 

24 

30 

36 

Maximum 
load  in 
1000  Ibs 

90 

140 

215 

285 

380 

480 

600 

720 

850 

1350 

1800 

54      RE-INFORCED  CONCRETE  CONSTRUCTIONS 

It  is  always  more  economical  to  use  larger  columns 
than  indicated  in  this  table. 

The  columns  can  be  made  of  any  shape,  rectangular, 
octagonal,  round,  etc.;  pipes  may  be  imbedded  for 
water,  gas  or  electric  wire  conduits. 


Fig.    35.— Sketch    Showing    the    Manner    in    which    Columns 
Fail. 

Reinforced  concrete  columns  are  nearly  30  per  cent 
cheaper  than  cast  iron  columns  without  fire  proofing 
and  are  much  more  reliable  than  the  latter,  proof  of 
which  we  cite,  the  test  at  the  S.  A.  Citadel  where 
a  girder  which  was  connected  on  one  side  to  a  girder 
and  on  the  other  side  to  a  column,  was  loaded  to  four 
times  the  capacity,  i.  e.,  100,000  Ibs.,  and  transmitted 
therefore  an  excentric  load  of  50,000  Ibs.  on  the 
column;  the  test  at  the  office  building  and  warehouse 
of  the  Davis  Sewing  Machine  Co.,  where  a  beam  of 
27  feet  span,  connected  at  one  side  to  a  ten  inch  column, 
produced  an  excentric  loading  of  62,000  Ibs.,  and  the 
very  severe  column  tests  made  at  the  Palais  de  Cos- 
tume at  the  last  Paris  Exhibition. 


RE-INFORCED  CONCRETE  COLUMNS  55 

The  building  was  entirely  constructed  in  armored 
concrete.  The  columns  were  twenty  feet  apart, 
and  of  such  small  diameter,  that  the  authorities  doubted 
their  resistance  to  eccentric  loading,  and  prescribed  a 
test,  consisting  in  a  load  of  sand  weighing  150  tons, 
or  one  and  one-half  times  the  load,  for  which  the 
columns  were  designed,  to  be  applied  on  alternate  panels 
of  the  two  stories  (Fig.  37).  The  lateral  spring  of 
the  columns  could  hardly  be  measured  and  was  a 
minute  fraction  of  1-32  of  an  inch. 

The  columns  are  concreted  in  forms,  consisting  of 
three  side  pieces,  while  the  fourth  side  is  left  open 


Fig.  36 
Forms  for  Columns. 


so   o -'---> 


£00 


Fig.  37. — Column  Test. 
Palais  de  Costume. 


(Fig.  36).  The  concrete  is  rammed  in  layers  of  a  few 
inches,  with  special  small  rammers,  and  the  open  side 
hoarded  up  as  the  concreting  progresses.  This  enables 
thorough  inspection  of  the  work  and  facilitates  the 
placing  of  the  ties  in  proper  distances. 

The  forms  may  be  struck  a  few  days  after  the  con 
crete  is  placed;  in  this  case  the  columns  should  be 
sprinkled  with  water    in    warm    weather  to  prevent 
where  no  plastering  is  required,  it  is  well  to  put  tri- 
checking  of  the  surface.    In  factories  and  warehouses, 


56      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


angular  strips  in  the  corners  of  the  forms,  to  obtain 
a  beveled  edge,  which  prevents  the  breaking  off  of  the 
otherwise  sharp  corners. 


<D      g 

-<  Si 


p| 

en 


RE-INFORCED  CONCRETE  COLUMNS 


58      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  COLUMNS 


59 


60      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  COLUMNS 


Gl 


62      RE-INFORCED  CONCRETE  CONSTRUCTIONS 
CONSIDERE   COLUMNS. 

By  inspecting  above  table  of  loads  for  various  sizes 
of  columns,  it  will  be  found  that  the  size  of  the  latter 
are  in  most  cases  smaller  than  the  size  of  fireproof  eel 
steel  columns.  There  exists,  however,  another  method 


or  f i  re-proofing 


SZCT/ON. 

ig.  44. — Considere  Columns. 

of  reinforcement,  by  which  the  size  of  the  columns  can 
be  very  considerably  reduced.  This  method  was  in- 
vented by  Mr.  Considere,  Chief  Engineer  of  the 
French  Government  Bureau,  for  the  investigation  of 
armored  concrete  construction.  He  made  thousands 


RE-INFORCED  CONCRETE  COLUMNS  63 


of  tests  on  round  concrete  columns,'  reinforced,  by 
jn  sizes  from  1-4  inch  to  3-4  inch,  which  were  wound 
in  .a  spiral  with  close  steps  around  the  surface  (Fig. 
44).  He  found  if  the  steps  of  the  spiral  is  less  than 
1-7  to  i-io  of  the  diameter,  that  such  columns  have 
without  any  longitudinal  reinforcement,  an  ultimate 
resistance  of  12,000  to  15,000  Ibs.  per  square  inch  of 
sectional  area  of  the  concrete. 

His  tests  also  indicate  that  if  we  reinforce  concrete 
by  spirals  and  by  longitudinal  rods,  we  can  safely  allow 
an  average  compressive  stress  of  three  to  four  thousand 
pounds  per  square  inch  on  these  columns,  which  would 
mean  that  a  20  inch  round  column  can  easily  carry  a 
load  of  one  million  pounds.  These  columns  do  not 
fail  by  shear,  but  by  bending  and  show  a  surprisingly 
great  ductility,  many  even  very  short  specimens  bend 
ing  into  an  "S"  shape,  when  the  ultimate  load  was 
reached.  They  give  ample  warning  before  failure, 
the  surface  of  the  concrete  begins  to  scale  long  before 
the  limit  of  capacity  is  reached.  There  is  no  doubt 
that  these  columns  will  be  extensively  used  for  heavy 
loads,  where  small  sized  columns  are  preferred.  It  is 
not  advisable  to  use  them  for  light  loads;  this  would 
reduce  the  size  of  the  columns  to  such  an  extent  that 
their  appearance  would  be  very  frail.  Besides  they 
are  much  more  expensive  for  smaller  loads  than  the 
square  or  rectangular  columns. 


64      RE-INFORCED  CONCRETE  CONSTRUCTIONS 


CO 

-£>. 
Oi 


RE-INFORCED  CONCRETE  COLUMNS 


65 


66 


RE-INFORCED  CONCRETE  CONSTRUCTIONS 


CONSTRUCTION      OF      REINFORCED      CON- 
CRETE  FOOTINGS. 

Fig.  48  shows  a  typical  wall  footing.  It  can  be  con- 
sidered a  cantilever  to  both  sides  of  the  wall  and 
figured  on  the  same  principle  as  floor  slabs.  The  height 
of  these  footings  rarely  exceeds  1-4  to  1-5  of  the 
width,  thus  saving  a  considerable  amount  of  excava- 
tion and  the  cutting  into  the  hard  crust  which  general!^ 
overlies  the  yielding  stratum.  In  connection  with 


^*  Steel  rod s> 


Fig.  48. — Reinforced  Concrete  Wall  Footing 

concrete  basement  walls,  these  footings  form  a  huge 
girder,  which  will  easily  transmit  the  wall  loads  to  a 
considerable  length,  should  one  part  of  the  soil  be  less 
resisting  than  another.  In  case  of  newly  filled  up 
ground  for  considerable  depth,  this  kind  of  foundation, 
if  only  1,000  to  1,500  Ibs.  pressure  per  square  foot  is 

67 


68        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

allowed  on  the  ground,  will  be  much  cheaper  and  very 
often  safer  than  pile  foundations.  Fig,  49  shows  a 
column  footing  designed  on  the  same  principles.  It 


Fig.  49. — Reinforced  Concrete  Column  Footing. 

can  be  considered  a  cantilever  on  four  sides  and  the 
steel  rods  cross  each  other  at  right  angles. 

The  largest  footing  built  on  this  order  is  a  square 
of  70  feet  length  of  sides. 

Figures  50,  51  and  52  show  quite  a  departure  in 
concrete  foundations.  They  illustrate  an  all-concrete 
warehouse 'with  floor  loads  up  to  800  Ibs.  per  square 
foot,  built  for  the  Co-operative  Wholesale  Society, 
Limited,  at  New  Castle-on-Tyne. 

The  building  rises  to  a  height  of  120  feet  above  the 
quay  level,  on  which  it  abuts,  and  consists  of  basement. 


RE-INFORCED  CONCRETE  FOOTINGS 


69 


ground  floor,  and  six  upper  floors,  being  in  all  eight 
stories  in  height  from  the  foundation  level  to  the  roof. 
It  occupies  a  frontage  of  92  feet  to  both  the  Quay  side 


Fig.  50. — Section    through    Armored    Concrete    [Ware-ihouse, 
New  Castle-on-Tyne. 

in  the  front  and  Sandgate  in  the  rear,  and  the  depth 
from  back  to  front  measures  125  feet. 

The  principal  difficulty  which  the  architect  of  the 
Co-operative  Wholesale  Society  had  to  face  was  that 
the  ground  at  the  site  of  the  building  was  of  the  worst 
description  imaginable  for  foundations.  It  consisted 
of  the  following :  Eighteen  feet  of  made  ground,  prin- 


70         RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  FOOTINGS  71 

cipally  clay;  eighteen  feet  of  silt  and  quicksand,  ten 
feet  of  soft  clay,  five  feet  of  hard  clay,  ten  feet  of 
silty  sand,  and  finally  of  gravel.  And  to  add  to  this 
difficulty,  the  above  stratification  had  a  pronounced  dip 
to  the  River  Tyne.  It  was  obvious  from  the  start 
that  the  foundations  would  have  to  be  of  an  abnormal 
character  to  carry  with  safety  the  enormous  weight 


Tig.  5. 


i.  52.—  Plan  of  a  Raft  Panel. 


superimposed  by  the  projected  building,  which  at  first 
it  was  intended  to  construct  of  brick  on  a  foundation 
of  cylinders  seven  feet  six  inches  in  diameter  sunk  to  . 
depth  of  sixty-two  feet  below  the  ground  level  of  the 
Quay  side  and  twenty  feet  below  the  ground  level  at  the 
Sandgate  side,  carrying  a  raft  of  concrete  four  feet 
thick,  with  rails  embedded  therein.  Another  alterna- 


72        RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  53. — Ware-house,  New  Castle-on-Tyne,     with   Floor   Loads 
of  800  pounds  per  square  foot. 


RE-INFORCED   CONCRETE  PILES  73 

tive  considered  was  the  driving  of  piles  to  the  same 
depth,  but  the  danger  of  injury  to  the  neighboring 
property  caused  that  method  to  be  abandoned.  Finally, 
the  Co-operative  Wholesale  Society  resolved  to  adopt 
their  architect's  recommendation  to  have  recourse  to  a 
raft  of  ferro-concrete  over  the  whole  area  of  the 
ground.  This  raft,  as  constructed,  measures  two  feet 
six  inches  in  its  thickest  part  and  only  seven  inches 
in  its  thinnest  part,  and  the  idea  of  sinking  piles  or 
cylinders  was  thus  abandoned,  it  being  found  that  the 
ferro-concrete  system  would  effect  a  great  saving  both 
in  cost  and  time. 

The  construction  of  the  raft  is  well  shown  in  Figs. 
51  and  52.  Each  column  rests  on  two  intersecting 
beams  2  ft.  5  ins.  by  2  ft.  6  ins.  deep,  which  divide  the 
area  of  the  building  into  rectangular  panels,  and  which 
beams  in  conjunction  with  concrete  arches,  seven  inches 
thick  in  the  center,  transmit  the  column  loads  over  the 
whole  available  area.  These  heavy  beams  are  able  to 
transmit  the  loads  for  several  panels,  if  there  is  a  set 
tlement  at  any  particular  point.  It  is  clear  that  b> 
making  these  girders  five  to  six  feel  deep,  we  can 
without  much  greater  expense  carry  the  column  loads 
over  two  to  three  panels,  even  if  the  ground  disappears 
under  a  whole  panel.  In  the  warehouse  mentioned 
an  unequal  settlement  took  place  between  the  date  of 
construction  of  the  footings  and  the  date  of  the  con- 
struction of  first  floor,  being  31-2  inches  in  the  front 
and  3  inches  in  the  rear.  Since  then,  no  further  settle- 
ment has  taken  place.  It  is  remarkable  to  note  that 
in  this  building  some  panels  of  200  sq.  feet  area  have 
been  tested  to  96  tons,  the  severity  of  which  test  will 
be  recognized  when  it  is  remembered  that  the  heaviest 


74        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

class  of  locomotive  with  tender  could  have  been  sup- 
ported on  a  floor  panel  14  feet  square. 

Fig.  54  shows  the  support  of  a  brick  wall  on  armored 
concrete  girders  and  columns,  which  is  a  very  econom- 
ical arrangement,  where  the  good  ground  is  found  at 
a  reasonable  depth  below  the  basement  floor. 


^  fMord  Crroynct 


Fig.  54.— Wall  carried  on  Isolated  Reinforced  Concrete  Piers. 


CONSTRUCTION      OF      REINFORCED      CON- 
CRETE PILES  AND  SHEET  PILES. 

Concrete  piles  have  great  advantages  over  wooden 
piles.  They  are  neither  affected  by  the  rise  and,  fall  of 
ground  water  or  by  sea  water,  nor  can  they  be  attacked 
by  torredoes,  which  in  certain  parts  of  the  world  de- 
stroy wooden  piles  in  a  very  short  time. 

These  piles  are  manufactured  in  molds,  at  least 
thirty  days  before  use  and  the  concrete  is  strengthened 
by  steel  rods  of  suitable  dimensions  connected  at  short 
intervals  by  stirrups  (Fig.  55).  At  its  lower  end  the 
pile  is  armed  with  a  pointed  shoe  with  side  plates, 
the  ends  of  which  are  turned  in,  so  as  to  lock  the  pile 
securely  in  place.  The  head  of  the  pile  is  of  less  width 
than  the  body,  allowing  a  clearance  between  the  heads 
of  two  adjacent  piles.  In  order  to  insure  uniform 
blows  from  the  hammer  in  process  of  driving,  and  to 
prevent  injury  to  the  pile,  the  head  is  protected  by  a 
cap  of  cast  steel  and  closed  at  its  lower  end  by  a  clay 
ring  held  by  a  plug  of  hemp  or  spun  yarn.  This  cap 
is  previously  filled  with  dried  sand.  A  very  regular 
cushion  is  thus  formed  on  and  all  around  the  head, 
which  cushion  distrubutes  the  pressure  in  an  absolute!) 
uniform  manner.  This  arrangement  renders  it  permis- 
sible for  the  iron  rods  to  project  beyond  the  head  of 
the  pile,  so  that,  in  case  of  need,  they  may  be  connected 
with  other  parts  of  the  structure  or  bent  into  hooks 
for  convenience  of  handling. 

75 


76        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

The  sheet  piles  (Fig.  56)  are  strengthened  by  foui 
rods,  connected  by  wire  clamps,  which,  in  their  turn, 
are  cross-tied  by  flat  irons.  At  the  lower  end  we  have 
again  a  shoe,  and  the  head  is  again  of  less  width  than 


Fig.  55. — Details  of  Reinforced  Concrete  Piles. 

the  body,  allowing  room  for  the  insertion  of  a  cap. 
About  6  inches  above  the  shoe  on  the  longer  of  the 
narrow  sides  a  projection  is  formed,  while  the  remain- 
der of  both  narrow  sides  is  grooved  for  the  entire 
length.  The  projection  on  one  of  the  piles  slides  in 
the  groove  of  the  'sheet  pile  last  driven  . 


RE-INFORCED   CONCRETE  PILES  77 

A  special  arrangement  is  provided  to  insure  the 
desired  direction  of  driving.  An  iron  pipe  which  fits 
the  groove  of  the  sheet  pile  last  driven,  and  that  of 
the  pile  which  is  being  driven,  connects,  by  means  of 
a  hose,  with  a  pump  or  water  tank.  This  pipe  serves 
as  guide,  and  the  water  forces  out  the  sand  which 
might  jam  the  grooves,  thus  facilitating  the  driving  of 
the  pile.  Once  the  pile  is  down  to  the  desired  depth, 


Fig.  56.— Details  of   Reinforced  Concrete  Sheet  Piles. 


78        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

the  pipe  is  withdrawn,  cement  is  run  between  the 
grooves  and  a  perfect  water-tight  joint  and  wall  are 
established.  Tongue  and  groove  joints  are  also  some- 
times used. 


Fig.  57 — Sheet  Piles,  retaining  bank  6 
These  are  splendid  members  of  construction  for 
marine  work  such  as  wharves,  docks,  jetties,  etc.  Of 
course,  such  structures  have  to  withstand  blows  from 
vessels,  but  owing  to  the  elasticity  of  reinforced  con- 
crete, the  damage  caused  is  certainly  less  than  in  the 
case  of  wooden  piles  and  can  be  more  easily  repaired. 

Masonry  as  applied  to  dock  and  harbor  work  pre- 
sents numerous  drawbacks,  amongst  those  commonly 
met  with  being  the  settlement  of  heavy  walls  owing  to 
the  instability  and  uncertainty  of  foundations.  In 
most  cases  they  rest  on  alluvial  .ground,  hence,  the 


RE-INFORCED   CONCRETE   PILES 


Fig.  58.— Driving  of  Reinforced  Concrete  Piles,  using  a  4,000 
pound  hammer.  Section  of  piles,  8  by  16  inches; 
length;  40  feet. 


80        RE-INFORCED  CONCRETE  CONSTRUCTIONS 


CD    01 

i  ? 


at 


d 
OP    " 


RE-INFORCED   CONCRETE  PILES  81 

frequent  practice  of  driving  wooden  piles  under  the 
walls  in  order  to  reach  a  better  and  firmer  stratum. 
The  necessity  for  driving  these  piles  to  great  depths 
largely  increases  the  cost  of  the  work  and  seriously 
impedes  the  operations  without  always  giving  satisfac- 
tory results. 


Fig.  60. — Barge-Quay  and  Jetty  in  course  of  construction. 

Should,  however,  a  masonry  wall,  as  above  de- 
scribed, remain  stable  as  regards  foundation,  and  the 
joints  resist  the  effect  of  the  waves,  it  nevertheless  often 
remains  exposed  to  the  effects  of  the  scouring  of  the 
ground.  To  remedy  this  latter  evil  it  is  customary  to 
enclose  the  work  by  wooden  sheet  piles,  but  their  ex- 
posed parts  rapidly  decay  or  are  destroyed  by  other 
agencies. 


82        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

The  use  of  reinforced  concrete  piles  and  sheet  piles 
obviates  these  evils.  The  following  are  the  principle 
advantages  claimed  for  these  piles  as  applied  to  sea 
work :  they  can  be  manufactured  in  any  practical 
length  and  section  and  they  can  be  driven  as  a  con- 


t 


Fig.  61. — Cross-section  of  Jetty. 

tinuous  pile  to  great  depths.  Sheet  piles  form  a  water- 
tight barrier  without  a  single  horizontal  joint,  which 
can  be  calculated  tCj  resist  any  pressure  that  is  brought 
to  bear  upon  it.  This  water-tight  wall  is  carried  down 
to  the  firm  stratum,  thus  preventing  any  disturbance 
that  might  take  place/  below  the  base  of  an  ordinary 
wall;  once  built  its  relative  lightness  is  such  that  it 
does  not  add  appreciably  to  the  original  density  of 
the  ground. 


RE-INFORCED   CONCRETE   PILES 


i 


84        RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  63. — Dagenham  Jetty  in  course  of  construction. 


Fig.  64. — Dagenham  Jetty  in  course  of  construction. 


RE-INFORCED  CONCRETE  WALLS  85 

The  piles  used  in  jetty  construction  are  braced  by 
struts  and  covered  by  a  reinforced  concrete  floor  strong 
enough  to  carry  the  super-imposed  loads,  railroad 
tracks  or  cranes,  which  may  be  imposed  upon  them.  It 
is  clear  that  the  cost  of  such  a  jetty  must  be  very  much 
lower  than  if  built  of  stone  or  solid  concrete. 


86        RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  66. —   Apartment  and  Office  Building,  Paris    France. 


CONSTRUCTION      OF      REINFORCED      CON- 
CRETE WALLS. 

Reinforced  concrete  walls  are  seldom  built  solid  in 
imitation  of  brick  walls,  where  they  have  to  support 
several  floors.  It  is  more  economical  to  transmit  the 
floor  loads  to  reinforced  concrete  columns,  which  form 


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Fig.  65. — Reinforced  Concrete  Wall. 

pilasters  in  the  walls,  and  are  therefore  only  curtain 
walls  (see  Fig.  65).     These  curtain  walls  are  subject 
to  very  little  stress ;  in  outside  walls  they  have  to  with 
stand  the  wind  pressure,  which  is  generally  figured  at 

87 


88        RE-INFORCED  CONCRETE  CONSTRUCTIONS 

30  Ibs.  per  sq.  foot.  To  prevent  cracking  .owing  to 
the  influence  of  change  of  temperature  we  have  to  make 
these  walls  three  and  one-halt  to  four  inches  thick,  and 
for  the  same  reason  they  have  to  be  reinforced  by  steel 
rods  in  both  directions,  which  reinforcement  is  more 
than  sufficient  to  take  care  of  the  wind  stresses.  These 
walls  are  of  great  importance  for  buildings  in  the 
business  district  of  our  large  cities,  where  each  front 
foot  has  a  valuation  running  into  many  thousands  of 
dollars ;  by  adopting  side  w^alls  4  inches  thick,  one  and 
one-half  to  two  feet  in  width  of  building  is  easily 
saved.  The  same  holds  true  for  storage-houses  which 
are  often  divided  up  by  a  large  number  of  brick  par- 
tition walls.  These  walls  are  also  much  lighter  than 
brick  walls,  having  a  weight,  in  fact  1-3  to  1-4  of  the 
latter,  thus  reducing  the  cost  of  foundation  consider- 
ably, especially  where  pile  driving  is  necessary.  It  is 
needless  to  point  out  that,  by  the  use  of  concrete  walls, 
we  obtain  a  rigidity  of  the  building,  which  cannot  be 
had  by  any  other  construction. 

Fig.  66  shows  a  highly  ornamented  reinforced  con- 
crete front  wall;  all  ornaments  are  cast  in  place  and 
monolithically  connected  with  the  wall  which  is  4 
inches  in  the  top  story  and  increases  to  7  inches  in  the 
first  story. 

This  is  by  no  means  an  easy  and  low  priced  con- 
truction;  only  specially  experienced  workmen  can  do 
an  acceptable  job;  and  it  is  much  easier  to  build  up 
such  a  front  of  separate  blocks  of  artificial  stone. 

If  only  a  simple  and  neat  front  is  required  without 
being  ornamental,  a  one  inch  cement  finish  is  applied 
to  the  wall;  this  also  is  not  an  easy  job  and  requires 
men  well  experienced  in  this  class  of  work;  for  ex- 


RE-INFORCED  CONCRETE  STAIRS 


89 


90         RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  STAIRS  91 

ample,  see  Fig.  67.  Sometimes  the  walls  are  finished 
by  rough  picking  them,  by  hand,  or  pneumatic  tools, 
a  week  or  so  after  concreting.  Fig.  68  shows  the 
application  of  armored  concrete  to  basement  walls. 
These  walls  are  required  to  withstand  the  horizontal 
pressure  from  the  earth  and  from  the  load  on  the 
ground  above  near  the  wall.  This  horizontal  pressure 
will  rarely  exceed  an  average  of  300  pounds  per  square 
foot,  for  the  depth  of  the  basement  in  general  use, 
and  by  inspecting  the  table  given  for  floor 
slabs,  it  will  be  found  that  it  is  rarely  necessary 
to  make  these  walls  more  than  6  inches  thick,  if  the 
pilasters  in  the  walls  are  spaced  10  to  15  feet.  It  is 
clear  that  these  pilasters,  w^hich  are  often  the  outside 
wall  columns,  are  subjected  to  bending,  and  must  be 
designed  accordingly. 

REINFORCED    CONCRETE    STAIRS. 

One  of  the  most  essential  features  of  a  permanent 
building  is  a  substantial,  fireproof  stairway.  For  this 
purpose  there  is  no  material  which  has  so  many  good 
properties  as  reinforced  concrete.  Compared  with  steel 
stairs,  reinforced  concrete  stairs  has  numerous  advan- 
tages, as  follows : 

First,  the  cost  can  be  reduced  to  one-half  of  that  of 
steel  construction,  with  decided  improvement  in  ap- 
pearance. 

Second,  they  are  absolutely  fireproof,  as  far  as  any 
known  material  can  be  made  to  attain  this  end. 

Third,  reinforced  concrete,  applied  to  stairs,  can  be 
molded  into  any  shape,  and  can  be  given  either  a  plain 
or  elaborate  finish. 

Fourth,  as  seen  from  below,  no  unsightly  structural 
steel  members  are  exposed,  the  soffit  of  concrete  stairs 


92         RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Fifth,  the  risers,  treads,  stringers  and  soffit  can  be  cov- 
presenting  a  clean  and  even  surface  ready  for  plaster- 
ing, 
ered  with  marble,  scagliola,  cement,  granolithic,  mo 


Fig.  69. — Stairs,   Cantilever   Galleries   and   Cable   Drive   in   a 
Spinning  Mill. 

saic  or  wood  finish,  and  in  fact  concrete  stairs  may  be 
treated  to  any  design  suitable  to  harmonize  with  the 
surroundings. 


RE-INFORCED  CONCRETE  STAIRS 


93 


At  the  ordinary  market  price  of  cut  and  polished 
marble  it  is  possible  to  build  a  concrete  stairway  cov- 
ered with  slabs  of  marble  at  less  cost  than  steel  stairs 
with  cast  iron  treads  and  rises. 


Fig.  70.— Fire  Escape,  Spinning  Mill.  "La  Cite,"  Strassburg. 

Reinforced  concrete  stairs  usually  consist  of  hori- 
^.ontal   floor   slabs   in   the   landings,    which   are   coi. 
nected  to  the  inclined  slabs  of  the  flights,  and  a  num- 
ber of  girders  supporting  these  landings  and  flights. 


94        RE  INFORCED  CONCRETE  CONSTRUCTIONS 

The  risers  and  treads  are  monolithically  connected  with 
the  slabs,  both  being  concreted  simultaneously.  Where 
the  free  spans  do  not  exceed  ten  feet  or  thereabouts, 
the  stairs  can  be  constructed  without  any  other  visible 


Fig.  71. — Staircase,  Salvation  Army  Building,  Cleveland,  O. 

support  than  the  slabs.  For  larger  spans  girders  must 
he  provided  to  support  landings,  and  stringers  must 
likewise  be  used  and  treated  as  girders. 

The  stringers  may  be  built  either  as  open  or  closed 
stringer;  two  to  four  inches  thick  will  be  ample  for 
ordinary  spans,  and  of  any  depth  to  meet  the  archi- 
tectural requirements.  Figs.  69  and  70  show  stairs 


RE-INFORCED  CONCRETE  STAIRS 


95 


built  up  of  concrete  slabs  without  stringers,  while 
Figs.  71  and  74  show  stairs  of  open  stringer  construc- 
tion, and  Figure  72  shows  a  closed  stringer  type. 


Fig.  72.— Staircase,  Ingall's  Building,  Cincinnati,  O. 

These  stairs  can  be  built  to  conform  to  any  geomat- 
rical  form  used  in  existing  staircase  construction  of 
other  material.  For  example,  for  winding  and  spiral 
stairs,  as  shown  in  Fig.  98. 


96        RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  73.— ^Looking  down  10   Flights   of  Stairs,  Power  Build- 
ing, Cincinnati,  O. 

The  cheaper  class  of  concrete  stairs  may  be  givea 
a  cement  or  granolithic  finish,  with  a  nosing  in  exact 
imitation  of  cut  stone  steps.  These  stairs  have  been 
adopted  in  numerous  school  bouses  and  public  build- 
ings in  England  and  France.  Where  the  stairs  are 
subject  to  considerable  travel,  the  treads  are  some- 
times inlaid  with  cubes  of  lead,  rubber  or  wood,  two 
to  three  inches  apart,  to  give  a  more  secure  footing, 
as  the  surface  otherwise  becomes  polished. 

The  material  for  railings  and  newel  posts  may  be 
cast  or  wrought  iron  or  other  metal,  wood,  cut  stone 
or  concrete.  The  railings  are  fastened  to  the  top 
of  the  stringers  or  treads  by  means  of  expansion  bolts, 
screwed  into  holes,  which  are  provided  in  the  con- 


RE-INFORCED  CONCRETE  SKELETONS  97 

struction  of  the  stairs,  or  by  bolts  which  are  imbedded 
in  the  triangular  face  of  the  steps,  where  there  are 
no  stringers,  or,  as  it  is  often  the  case,  the  railing 


Fig.  74. — Concrete    Staircase,  Cantilever  Galleries  and  Ceiling 
in  a  Department  Store. 

is  only  fastened  to  the  newel  posts.  For  the  latter, 
sockets  are  left  in  the  landings  and  lower  and  upper 
treads,  as  required,  in  identical  manner  as  in  wood 
construction. 


REINFORCED  CONCRETE  SKELETON  BUILD- 
INGS 

Reinforced  concrete  skeleton  building  construction 
will  scon  come  into  universal  use  for  high  office  build- 
ings, hotels,  ware-houses,  etc.,  on  account  of  the  great 
economy  this  type  of  construction  offers  to  the  publh 


Fig.  75. — Reinforced  Concrete  Skeleton    of    a     Flour     Mill. 
Columns,  27  feet  on  centers. 

compared  with  steel  construction,  even  meeting  the 
competition  of  wood  construction.  We  understand  by 
skeleton  construction,  a  frame  composed  of  columns 

98 


RE-INFORCED  CONCRETE  SKELETONS 


99 


Fig.  76.— MacDonald  &  Kiley's  Shoe  Factory,  Cincinnati,  O. 
Reinforced  concrete  skeleton  construction.  8  inch 
brick  fillings. 

and  girders  supporting  all  the  outside  walls,  from 
story  to  story,  making  it  possible  to  reduce  the  thick- 
ness of  the  walls  to  a  minimum  in  each  story.  This 
arrangement  gives  increased  floor  space,  and  reduces 
the  weight  of  the  walls  as  well  as  the  cost  of  founda- 
tion. 

The  outside  walls  being  reduced  to  curtain  walls, 
their  thickness  in  high  office  and  hotel  buildings  is  cfe- 
pendent  on  the  architectural  treatment,  though  usually 
12  inches  thick,  while  in  ware-houses  and  factories,  8 
inch  walls  are  sufficient.  In  hotel  and  office  buildings 


100     RE-INFORCED   CONCRETE  CONSTRUCTIONS 

the  columns  and  lintels  are  always  lined  with  stone, 
brick  or  terra  cotta^and  for  this  purpose  anchors  are 
imbedded  in  the  concrete  columns  and  3  1-2x2  1-2 
x  1-4  inch  angles  are  bolted  to  the  lintels,  as  shown  in 
Fig.  77.  In  ware-houses  and  factories  the  column^ 
and  girders  can  be  left  exposed  to  view,  and  finished 


r\ '. . .  •  -  r . 

r  _!>. ."  ' ,' 


Fig.   77. — Detail   showing  Brick  Anchoring  of  Brick  Facing 
to  Concrete   Lintels  and  Columns. 

by  rough  picking  or  by  cement  mortar  in  imitation  of 
cut  stone  columns  and  lintels.  The  curtain  walls  are 
erected  on  the  upper  surface  of  the  lower  lintels  and 
extend  from  column  to  column,  are  carried  up  to  the 
lower  surface  of  the  upper  lintel,  thus  covering  the 
entire  panel  except  where  openings  for  windows  are 
required.  Brick  curtain  walls  can  be  replaced  with 
economy  by  walls  of  hollow  concrete  blocks,  and  we 
thus  obtain  an  all-concrete  construction.  There  are, 
however,  only  very  few  concrete  blocks  which  we  have 
found  satisfactory ;  most  of  those  on  the  market  rapid- 


RE-INFORCED  CONCRETE  SKELETONS          101 

ly  absorb  water  and  should  not  be  used.  A  very  satis- 
factory block  is  made  by  Mr.  Charles  W.  Stevens,  of 
Harvey,  111.;  it  is  also  claimed  that  the  blocks  manu- 
factured by  hydraulic  pressure  do  not  absorb  water; 
there  may  be  other  satisfactory  blocks  on  the  market, 
unknown  to  the  writer. 

Four  inch  reinforced  concrete  walls  can  also  be  us^d 
but  they  are  more  expensive  than  8  inch  brick  or  con- 
crete block  walls.  In  an  all-concrete  building  all  the 
columns,  footing  of  columns,  basement  walls  (see  Fig. 
68),  girders,  beams,  lintels,  floors,  roofs  and  stairs 
are  built  of  reinforced  concrete,  while  the  walls  ma} 
be  of  reinforced  concrete  or  concrete  blocks. 

Tile  or  reinforced  plaster  partitions  are  less  expen- 
sive than  armored  concrete  partitions.  The  latter, 
however,  can  withstand  the  action  of  fire,  impacts  from 
streams  of  water  or  falling  objects  much  better  than 
the  former,  and  should  be  adopted,  where  it  is  of 
great  importance  to  prevent  the  spread  of  fire  from 
one  part  of  a  building  to  the  other.  Stair  case  and  ele- 
vator walls,  as  well  as  fire-proof  vaults  should  be  built 
of  concrete  instead  of  hollow  brick,  as  heretofore 
universally  used.  We  find  in  nearly  every  great  fire, 
that  the  brick  walls  crack  and  fall ;  it  is,  however,  safe 
to  say  that  a  vault,  built  from  the  foundations  up  of 
6  to  8  inch  concrete  walls,  heavily  reinforced  by  steel 
rods,  will  withstand  the  severest  conflagration  and  re- 
main intact  even  where  the  surrounding  walls  of  the 
building  collapse  and  cover  the  vault  with  the  debris. 


102     RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  SKELETONS         103 


104     RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  80.— Cotton  Spinning  Mill,  Strassburg,  Alsace. 


RE-INFORCED  CONCRETE  SKELETONS 


105 


106     RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED  CONCRETE  SKELETONS         10? 

Fig.  78  shows  a  flour  mill  in  Brest,  France,  built 
entirely  of  armored  concrete;  the  building  site  con- 
tained quick  sand  to  a  considerable  depth  and  concrete 
pile  foundations  were  resorted  to  as  the  most  feasible 
method  to  obtain  a  suitable  foundation ;  nevertheless  it 
settled  considerably,  as  much  as  12  to  18  inches  in 
parts,  causing  several  beams  and  floor  slabs  to  crack; 
however,  it  safely  carries  the  heavy  live  loads  imposed 
by  the  use  of  the  building,  and  this  can  only  be  ascribed 
to  the  use  of  stirrups  in  the  girders. 

Figs.  79  to  82  show  a-  cotton  spinning  mill  in 
Strassburg,  Alsace,  constructed  entirely  of  armored 
concrete.  This  building  is  140x140  feet  and  three 
stories  high.  The  columns  are  24  feet  on  centres  in 
both  directions  and  serve  as  supports  for  lines  of 
shaftings. 

Figs.  8 1  and  82  show  a  novelty  in  mill  construction, 
the  line  of  shaftings  being  supported  between  the 
columns  by  reinforced  concrete  hangers,  which  have 
proven  to  be  much  more  rigid  than  cast  iron  hangers. 
It  must  be  noticed  that  this  building  is  unusually  well 
lighted,  which  could  not  have  been  attained  by  any 
other  form  of  fireproof  construction. 


108     RE-INFORCED   CONCRETE  CONSTRUCTIONS 


Fig.  83.— Cotton  Spinning  Mill,  Lille,  France. 


RE-INFORCED  CONCRETE  SKELETONS 


109 


Fig.  84. — Eleven  Story  Audit  Office,  Paris,  France. 

Fig.  84  shows  the  n -story  Audit  office  of  the 
French  government,  having  a  reinforced  concrete  skel- 
eton. All  fireproof  vaults  in  this  building  are  of  con 
crete ;  since  this  modern  construction  has  been  adopted 
by  a  government  of  one  of  the  first  civilized  countries 
for  such  an  important  structure,  it  must  have  proved 
first  class  in  every  respect,  and  should  amply  meet  the 
requirements  of  private  buildings. 


The  highest  reinforced  concrete  skeleton  building  is 
the  1 6-story  Ingalls'  building,  in  Cincinnati,  O.,  erected 


110  RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  85.— Ingall's  Building,  Cincinnati,  O. 


RE-INFORCED  CONCRETE  SKELETONS         HI 

in  1903.  It  is  50x100  feet  and  210  feet  high  above  the 
curb  line.  This  building  was  very  rapidly  erected, 
averaging  eleven  days  per  story.  Each  floor  formed  a 
perfect  roof,  under  which  all  plastering,  piping,  wir- 
ing and  interior  finish  was  carried  on,  whereby  much 
time  was  saved  over  other  methods  of  construction 
The  idea  of  constructing  a  high  office  building  in 
armored  concrete  was  considered  such  a'  novelty  in  this 
country  that  the  Cincinnati  Inspector  of  Buildings 
withheld  the  building  permit  for  many  months. 

A  wasteful  amount  of  steel  and  concrete  was  eventu- 
ally used  in  the  construction,  to  overcome  the  objec- 
tions of  the  city  authorities;  and  the  Ingalls'  building 
is  probably  the  strongest  high  building  ever  erected  in 
this  country:  with  nil  this  waste  of  material  a  notable 
economy  over  the  ordinary  tvpe  of  steel  skeleton  con- 
struction was  obtained,  and  the  time  of  erection  was 
also  considerablv  reduced.  Messrs.  Flzner  &  Anderson 
were  the  architects.  W.  H.  "Ellis  &  Co..  the  general  con- 
tractors, and  the  Ferro-Concrete  Co..  of  Cincinnati, 
the  contractors  for  the  reinforced  concrete  work. 

From  every  point  of  view  armored  concrete  buildings 
are  superior  to  those  of  any  other  type.  Thev  are 
monolithic ;  settlement  of  the  ground  is  properlv  trans- 
ferred and  equalized  by  their  enormous  rigidity;  they 
practically  consist  of  one  material  and  variation  of 
temperature  cannot  produce  unsightly  cracks;  they 
become  stronger  with  age,  concrete  forming  an  artificial 
stone  better,  than  the.  best  stone  which  ever  came  out  of 
a  quarry.  Considering,  moreover,  the  facility  with 
which  the  material  can  be  procured,  so  that  a  few 
months  are  needed  to  erect  the  largest  building,  to- 
gether with  the  surprisingly  low  cost,  it  must  be  evi- 
dent that  the  time  of  steel  skeleton  buildings  with  all 


112    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

their  flimsy  lug  and  bracket  connections,  their  insuffi- 
ciently protected  columns  and  their  high  cost,  is  rapidly 
passing  and  must  shortly  give  way  to  a  far  superior 
type,  namely,  armored  concrete  construction. 

The  reader  undoubtedly  desires  to  know  how  the 
cost  of  this  modern  type  of  construction  compares  with 
that  of  skeleton  steel  construction.  It  depends,  of 
course,  on  the  cost  of  the  materials,  cement,  sand, 
crushed  stone  and  steel  rods,  varying  in  different  lo- 
calities. Generally  speaking,  an  all-concrete  factory 
or  ware-house  can  be  built  for  from  7  to  8  cents  a 
cubic  foot,  based  upon  the  cubic  contents  of  the  build- 
ing, and  does  not  include  windows,  doors  or  interior 
finish. 

For  hotel  and  office  buildings,  the  concrete  skel- 
eton including  all  foundations,  floors,  roof,  basement 
walls  and  stairs  can  be  built  for  from  6  to  7  cents  a 
cubic  foot,  which  figures  will  be  found  to  be  from  25 
to  40  per  cent  lower  than  for  steel  construction,  de- 
pending upon  the  price  of  structural  steel. 

VIBRATIONS    IN    ARMORED   CONCRETE    STRUCTURES. 

The  monolithic  character  of  an  armored  concrete 
buildings  is  evidence  that  vibrations  produced  by  im- 
pacts, or  working  machinery,  will  be  much  smaller 
than  in  any  other  class  of  buildings.  Any  particular 
point  of  the  structure,  which  is  affected  by  an  impulse, 
brings  into  oscillation  every  part  around  it,  vibrating 
a  large  mass  of  great  rigidity;  therefore,  the  oscilla- 
tions must  be  far  less  than  in  steel  or  wood  structures, 
where  the  beams  and  arches  are  only  loosely  connected, 
and  can  be  set  in  vibration  independent  of  other  parts 
of  the  building.  We  have  seen  how  small  the  deflection 


RE-INFORCED  CONCRETE  SKELETONS         113 


Maximum  Elastic  Deflection  in  Inches  of  5ym- 

with  an  equally  distributed  load  (W)  and  strained  to  16,000 
.01655  -    when   L=span  in  feet,  d,  depth  of  girders  in 


Depth  of 
Girder 
in 
Inches. 

SPAN  IN  FEET. 

4 

6 

8 

10 

12 

14 

16 

18 

20 

22 

24 

4 

.0661 

.149 

.265 

.414 

.595 

.810 

1.06 

5 

.0529 

.119 

.212 

.331 

.476 

.648 

.845 

1.07 

1.32 

6 

.0441 

,0993 

.177 

.276 

,3fl7 

.540 

.707 

,891 

1,10 

1.33 

7 

.0379 

.0851 

.152 

.237 

.340 

.465 

BOTMM^ 

.606 

,766 

.946 

1.14 

1.36 

8 

.0331 

.074 

.132 

.207 

.298 

.405 

.530 

.670 

.829 

1.000 

1.19 

9 

,0295 

.0662 

.118 

.184 

.246 

.361 

.471 

.596 

,737 

,890 

1,06 

10 

.060 

.106 

.165 

.240 

.326 

.425 

,540 

.667 

,807 

,960 

11 

.054 

.096 

.150 

.216 

,295 

.385 

.486 

.600 

.725 

,862 

12 

.050 

.088 

.138 

,198 

.270 

,353 

,447 

.550 

,668 

.781 

13 

.046 

.081 

,127 

1,84 

.250 

.325 

,412 

,610 

,617 

,732 

14 

.075 

.118 

.170 

.232 

.302 

.383 

.472 

,572 

.680 

16 

.070 

.110 

.159 

.216 

.282 

,357 

.440 

.530 

,632 

16 

.066 

.104 

.149 

.203 

.265 

.335 

,413 

,500 

,596 

17 

.062 

.097 

.140 

.191 

.250 

.315 

.390 

,471 

,560 

18 

.059 

.092 

.132 

.180 

,235 

,297 

,368 

.445 

.530 

19 

.056 

.087 

.126 

.171 

.223 

,282 

.349 

.422 

.501 

20 

.053 

.083 

,119 

.162 

.212 

,267 

.331 

,400 

.477 

21 

.079 

.114 

.155 

.202 

,255 

.315 

.381 

.454 

22 

.075 

.108 

.147 

.192 

.244 

,300 

,365 

.432 

24 

.069 

.100 

.135 

.176 

.223 

.276 

.335 

.396 

26 

.064 

.092 

.125 

.162 

.206 

.255 

.309 

.365 

28 

.059 

.085 

.116 

.152 

,191 

,236 

.286 

.340 

30 

.055 

.080 

.108 

,141 

.179 

.221 

.267 

.318 

35 

.068 

.093 

.122 

.154 

.190 

.230 

,274 

40 

.081 

.106 

.134 

,165 

,200 

.238 

45 

,147 

,178 

,211 

50 

.190 

55 

60 

Deflections  at  right  of  heavy  broken  will  cause  plaster 
For  a  concentrated  load  in  center  of  span  reduce  figures 

For  any  other  fibre  stress,  13,000  Ibs.,  for  example 


metrical,  Freely  Supported  Steel  Girders. 

Ibs-  per  square  inch,  obtained  by  the  formulaD^oo*  ^T  = 
inches. 


SPAN  OT  FEET. 

Depth  of 
Girder 
in 
Inches. 

26 

28 

30 

32 

34 

36 

38 

40 

45 

50 

60 

4 

5 

7 

1.40 

8 

1.24 

1.44 

9 

1.12 

1.30 

1 

10 

1.02 

1.18 

1.35 

11 

.930 

1.08 

1.24 

1,40 

12 

.860  1.00 

1.14 

1.30 

13 

.800 

,92"i 

1.06 

1.20 

1,36 

14 

.741 

.863 

.9QQ 

1.12 

1.27 

15 

.700 
.658 
.621 

.810 
.762 
.720 

.930 
.876 
.829 

1.06 
1.00 
,940 

1.19 
1,13 

1.34 
1,96 

K^BW 

16 
17 
18 

1.06 

1,19 

.589 

.682 

.784 

,890 

1.00 

1,13 

1.26 

19 

.560 

.650 

.745 

.845 

.950 

1.07 

1.19 

T.32 

20 

.531 
.508 

.620 
.590 

,710 
.677 

,805 
,770 

,905 
.865 

1.02 
.970 

1.14 
1.08 

1.26 
1,20 

L60 
1.53 

1.R8 

21 
22 

.467 

.540 

.620 

,705 

.792 

,890 

1.000 

1,10 

1,40 

1.72 

2.50 

21 

.430 

.500 

,572 

,650 

,730 

.820 

,920 

1.02 

1.29 

1.59 

2.25 

•  26 

4.00 

.463 

.531 

,602 

,680 

.765 

.850 

.945 

1,20 

1.48 

2.12 

28 

.363 
.320 

.432 
.375 

.498 
.429 

,563 
,485 

.635 
.550 

,715 
,615 

,800 
.685 

.882 
.760 

1,12 
.960 

1.38 
1.18 

1.99 
1.70 

30 
35 

.230 

.325 

.362 

.422 

.476 

,537 

.600 

.661 

.838 

1.03 

1.49 

40 

.248 

.287 

.330 

,376 

.422 

,477 

.530 

.590 

.745 

.920 

1.32 

45 

.223 

.260 

.298 

,337 

.380 

,430 

,480 

,530 

,670 

.826 

1.19 

50 

.204 

.237 

.271 

,307 

,348 

,390 

,435 

,481 

,610 

,752 

1.08 

55 

.248 

,281 

,317 

,355 

.397 

.440 

,558 

,688 

,99 

60 

to  crack, 
by  1-5. 

multiply  abcmffigures  by 


116    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

of  armored  concrete  girders  is  under  static  loads  and  in 
comparing  this  deflection  with  the  deflection  given  in 
the  accompanying  table  for  steel  beams,  it  will  be 
found  they  are  often  only  1-5  to  i-io  of  the  latter. 

We  cite  a  very  interesting  comparative  experiment 
made  at  two  stations  of  the  Orleans  R.  R.  in  Paris. 

A  Amr.  concrete  floor,  figured  to  carry  a  machinery 
load  of  280  pounds  per  square  foot,  of  a  span  of  about 
1  6  feet,  was  subjected,  for  a  length  of  17  feet,  to  a  load 
of  420  pounds  per  square  foot.  The  maximum  deflec- 
tion was  1-8  inch,  without  any  permanent  set.  In  order 


Fig.  87.  —  Vibration  Diagrams. 

to  compare  the  resistance  of  this  floor  to  shocks  with 
that  of  steel  girder  floors,  this  floor  and  a  floor  of  the 
Quay  d'Orsay  station,  built  for  the  same  purpose  and 
of  the  same  span,  but  consisting  of  I  beams  and  brick 
arches,  were  subjected  to  the  impact  of  falling  weights. 
The  dead  weight  of  the  Amr.  concrete  floor  was  60 
pounds  per  square  foot,  that  of  the  other,  96  pounds 
per  square  foot.  A  weight  of  no  pounds,  falling  from 
a  height  of  6  1-2  feet,  produced  in  the  steel  and  brick 
floor,  vibrations  of  an  amplitude  of  5-32  inches,  lasting 
two  seconds,  while  a  weight  of  220  pounds,  falling 
from  a  height  of  13  feet  on  the  concrete  floor, 
caused  a  maximum  vibration  of  only  1-32  of  an  inch, 


RE-INFORCED  CONCRETE  SKELETONS 

lasting  5-7  of  a  second.  Thus,  twice  the  weight  falling 
twice  the  height,  caused  only  one-fifth  of  the  deflection, 
with  vibrations  lasting  only  a  third  of  the  time  (See 
Fig.  87). 

This  is  of  great  advantage  in  bridges,  and  especially 

in  factory  buildings,  not  only  because  the  lives  of  such 

structures  are  threatened  by  vibration,  but  also  because 

-  absence  of  vibration  preserves  the  tools  and  makes 

better  work  possible. 


FIREPROOF     QUALITIES     OF    REINFORCED 
CONCRETE. 

Concrete  is  the  best  fireproof  material  for  building 
purposes.  This  was  demonstrated  over  ten  years  ago 
by  comparative  tests  by  the  fire  departments  of  the 
cities  of  Vienna  and  Berlin;  more  recently  by  the  fire 
tests  conducted  by  the  British  Fire  Prevention  Com- 
mittee, and  by  the  very  careful  and  severe  tests  on  a 
score  or  more  reinforced  concrete  floors  by  the  building 
department  of  the  city  of  New  York. 

In  the  latter  city  for  each  test  a  house  10x14  feet  in 
the  clear,  and  about  12  feet  high,  was  built  and  covered 
by  the  concrete  floor  to  be  tested.  The  interior  of  the 
house  was  filled  with  coal  and  wood,  and  for  five 
hours  a  temperature  of  over  2,000  degrees  Fahrenheit 
was  maintained,  and  then  a  stream  of  water  from  the 
nozzle  of  a  steam  fire  engine  was  directed  for  a  few 
minutes  on  the  ceiling.  All  the  floors  stood  the  tests 
remarkably  well,  supported  the  uniformly  distributed 
load  of  150  Ibs.  per  square  foot  without  undue  deflec- 
tion, and  with  the  exception  of  a  few  fine  hair  cracks, 
which  disappeared  af'ur  cooling  off,  no  damage  what- 
ev^r  was  done  to  the  floors.  On  the  other  hand  we 
know  unprotected  steel  behaves  worse  in  a  severe  fire 

118 


FIREPROOF  QUALITIES  OF  CONCRETE 


120    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

than  heavy  mill  construction.  It  twists  and  warps 
into  various  shapes  after  a  temperature  of  1,000  de- 
grees Fahrenheit  is  reached.  This  was  demonstrated 
by  the  fire  at  the  works  of  the  Pacific  Borax  Com 
pany's  plant  at  Bayonne,  N.  J.,  in  1902.  Part  of  the 
plant  was  of  all-concrete  construction,  and  the  annex 
was  of  unprotected  steel  construction.  The  annex 
was  a  distorted  mass  of  iron  after  the  fire,  while  the 
concrete  building  stood  the  trial  exceedingly  well,  re- 
quiring only  plastering  to  restore  it  to  first  class  order, 
The  heat  in  the  latter  was  great  enough  to  melt  copper 
and  cast  iron. 

We  also  cite  a  fire  test  made  by  the  Belgian  Govern- 
ment and  Mr.  Hennebique  on  a  two-story  pavilion 
erected  for  this  purpose  at  Ghent,  Belgium. 

This  pavilion,  measuring  20x15  feet,  was  built  en- 
tirely of  ferro-concrete,  and  the  windows  and  doors 
were  provided  with  Siemens  wire  glass.  In  all,  two 
tests  were  made.  In  the  first  test  the  second  floor  was 
loaded  with  300  pounds  per  square  foot,  or  one  and  a 
half  times  the  load  for  which  it  was  designed,  and  a 
deflection  of  1-3,000  of  the  span  was  produced.  On 
the  Qth  of  September,  about  220  cubic  feet  of  wood 
and  coal  were  placed  in  the  lower  room.  This  material 
was  sprinkled  with  petroleum  and  set  on  fire.  The  con- 
flagration lasted  one  hour,  and  produced  a  temperature 
of  about  1,3000  degrees  Fahrenheit.  The  walls  were 
red  hot  on  the  inside;  yet,  notwithstanding  that  their 
thickness  was  only  4  3-4  inches,  the  hand  could  easily 
be  held  on  the  outside  without  experiencing  any  dis- 
comfort. 

The  temperature  of  the  second  floor  increased  only 
4  degrees,  which  means  that  no  mercantile  product 
whatsoever  would  have  suffered  damage.  The  deflec 


FIREPROOF  QUALITIES  OF  CONCRETE          121 


4> 

C 

c. 
Pk 


o"  3 

-M      CO 

CO 


§1 
E  § 


122    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

tion  of  the  floor  increased  to  6-10  of  an  inch,  but  two 
hours  after  the  extinction  of  the  fire,  was  diminished  by 
half  an  inch,  so  that  under  a  very  heavy  load  the  per- 
manent deflection  resulting  from  the  fire  was  scarcely 
perceptible. 

In  order  to  prove  that  an  armored  concrete  floor, 
which  had  been  subjected  to  fire,  was  still  capable  of 
bearing  the  same  loads  as  before,  Mr.  Hennebique 
made  a  new  test  on  the  28th  of  September;  this  time 
loading  the  floor  with  400  pounds  per  square  foot,  or 
double  its  figured  load.  When  the  300  pound  mark 
was  reached  the  deflection  was  found  to  be  precisely 
the  same  as  before  the  first  fire  test.  At  400  pounds 
per  square  foot  the  deflection  was  only  1-8  of  an  inch. 

The  lower  room  was  completely  filled  with  wood 
and  coal,  the  upper  room  partially  filled  with  the  same 
materials,  and  the  roof  was  loaded  with  200  pounds 
per  square!  foot.  At  six  minutes  past  four  the  fire  was 
lighted  on  both  piles  and  lasted  until  half  past  six.  The 
fire  played  so  fiercely  against  the  sides  and  ceiling  that 
the  plastering  of  the  latter  was  calcined,  and  the  wire 
glass  of  the  windows  and  doors  melted. 

The  building  was  momentarily  forced  out  of  shape 
(expanded),  but  showed  no  cracks  and  only  very  fine 
fissures,  which  in  no  case  permitted  the  hot  air  to 
escape.  Again  the  contact  of  the  hard  to  the  outside 
of  the  walls  could  easily  be  endured.  The  deflection 
of  the  second  floor  reached  a  maximum  of  3-4  inch  at 
20  minutes  to  six;  after  this  time  no  further  increase 
could  be  observed. 

At  half  past  six,  when,  after  continual  firing,  no 
change  in  the  state  of  the  building  could  be  detected, 
the  commission  agreed  to  extinguish  the  fire,  which 
was  done  by  directing  a  stream  of  water  from  a  hose 


|TQ  ^  fSjJ^X 

FIREPROOF  QUALITIES  t>fCONCRETE          123 

against  the  walls  and  ceiling  and  against  the  hot 
coal. 

When,  on  the  following  day,  the  fire  authorities 
examined  the  building,  it  was  found  that  the  conflagra- 
tion had  not  injured  the  general  structure  in  any  way. 
There  was  no  permanent  set  in  the  floors  and  the  few 
fissures  caused  by  the  expansion  were  completely 
closed.  A  series  of  pyrometers  indicated  a  temperature 
of  2,200  degrees  Fahrenheit. 

Lime  kilns,  constructed  entirely  'of  concrete,  have  en- 
dured for  years  a  tempera'ture  of  2,200  to  2,500  degrees 
Fahrenheit. 

All  these  fire  tests  are  of  little  importance  in  com- 
parison with  the  fire  tests  which  steel  skeleton  buildings 
with  terra  cotta  fire-proofing,  and  concrete  steel  skele- 
tons had  to  withstand  in  the  terrible  Baltimore  con- 
flagration on  the  7th  and  8th  of  February,  1904, 
which  continued  for  27  hours,  and  destroyed  2,50x3 
buildings. 

The  steel  skeleton  buildings  failed  badly,  on  very 
few  columns  and  girders  remaining  intact,  the  terra 
cotta  floors  being  destroyed  very  often,  and  all  ex- 
perts who  visited  the  burnt  district  agree  that  no  build- 
ing resisted  this  fire  of  27  hours  better  than  the 
Junker's  Hotel  and  the  International  Bank  Build- 
ing, built  entirely  of  reinforced  concrete,  undei 
the  direction  of  Messrs.  Parker  &  Thomas,  Arch- 
itects of  Baltimore.  The  columns,  girders,  and  floors 
remained  perfectly  intact,  though  the  contents  were 
entirely  consumed.  The  fire  around  this  building  was 
so  intense  that  even  the  brick,  which  elsewhere  held 
out,  were  entirely  destroyed. 

Reinforced  concrete  buildings  will  now  undoubted- 
ly command  lower  rates  of  insurance  than  buildings 


124:    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

of  the  same  class  erected  on  the  old  style  of  steel  and 
terra  cotta  construction. 

The  superior  fire  resisting  properties  of  armored 
concrete  as  demonstrated  in  the  most  terrible  conflagar  • 
ation  at  Baltimore  deserves  the  careful  consideration  of 
Architects,  Engineers,  and  their  clients,  who  are  con- 
sidering the  investment  of  capital  in  fire  proof  struct- 
ures. 

PROPERTIES  OF  THE  COMBINATION  OF  CONCRETE 
AND  STEEL. 

Many  eminent  scientific  men  have  investigated  the 
properties  of  armored  concrete  and  established  the  fol- 
lowing facts  explaining  the  great  success  of  the  com- 
bination of  concrete  and  steel : 

First,  the  coefficient  of  expansion  of  concrete  and 
steel  is  for  all  practical  purposes  the  same,  therefore, 
no  interior  stresses  can  be  produced  by,  change  of  tem- 
perature, either  in  the  steel  or  surrounding  concrete. 

Second,  there  exists  a  surprisingly  large  adhesion 
between  concrete  and  steel,  amounting  from  500  to 
700  pounds  per  square  inch  of  surface  in  contact. 
Much  doubt  has  been  expressed  regarding  this  ad- 
hesion ;  it  is  however  confirmed  by  hundreds  of  experi- 
ments here  and  abroad.  Slight  rust  on  the  surface  of 
'the  imbedded  bar  increases  this  adhesion  by  about  10 
per  cent.  Corrugating  or  twisting  of  bars  also  in- 
creases it  to  10  per  cent. 

Third,  the  modulus  of  elasticity  of  steel  is  ten  to 
twenty  times,  and  if  the  concrete  is  highly  stressed  it 
is- about  100  times  as  great  as  the  modulus  of  elasticity 
of  concrete.  It  will  be  asked  how  it  is  possible  to 
figure  reinforced  concrete  structures  if  such  differences 


FIREPROOF  QUALITIES  OF  CONCRETE         125 

exist.  We  must  admit  that  the  modulus  of  elasticity 
varies  with  the  amount  of  water  and  cement,  the 
tamping,  etc.,  but  all  concretes  show  the  fundamental 
fact  that  the  modulus  of  elasticity  decreases  the  higher 
the  stress,  and  is  nearly  zero  at  300  pounds  per  square 
foot — that  is  at  the  ultimate  resistence  of  non-rein- 
forced concrete.  That  is  to  say,  in  a  concrete  bar 
reinforced  by  steel  and  subjected  to  tension  stresses 
exist  in  the  concrete  and  the  steel  which  are  in  the 
relation  of  i  to  10,  to  i  to  20,  at  moderate  stresses, 
and  when  the  bar  is  highly  stressed,  in  the  relation  i 
to  loo,  whatever  the  modulus  of  elasticity  be  at  the 
lower  stresses. 

This  means  that  reinforced  concrete  stretches  con- 
siderably at  300  pounds  stress  by  the  least  increase  of 
tension,  and  this  elongation  can  reach  the  elongation 
of  steel  at  the  elastic  limit  and  amounts  to  about  I  in 
1,000.  It  will  now  be  understood  why  reinforced  con- 
crete girders  and  slabs  deflect  considerably  before 
breaking,  while  we  know  that  non-reinforced  concrete 
breaks  without  practically  any  deflection. 

This  will  also  explain  why  reinforced  concrete  can 
be  used  for  water  tanks,  sewers  and  roofs,  which  must 
undergo  great  changes  of  lengths  through  the  constant 
changes  of  temperature,  the  steel  giving  the  concrete 
an  exceedingly  great  elasticity  whereby  it  can  undergo 
these  changes  without  danger  of  cracking. 

Fourth,  the  steel  is  completely  protected  by  the  con 
crete  from  rust  and  the  disintegrating  effect  of  air 
and  water,  sea  water,  or  even  sulphuric  or  chlorine 
gases.  We  know  that  iron  nails  were  preserved  by  the 
mortar  of  Roman  walls  for  2,000  years,  and  we  have 
not  even  the  least  reason  to  doubt  that  the  far  superior 


126    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

Portland  cement  will  show  the  same  preservative 
qualities.  In  order  to  remove  any  doubt  on  the  ques- 
tion of  the  preservation  of  steel  in  concrete,  engi- 
neers induced  the  city  authorities  of  Grenoble, 
France,  to  take  up  a  water  main  of  armored  concrete, 
which  had  been  in  constant  service  for  a  period  of  15 
years  under  a  head  of  75  feet  of  water.  The  sec- 
tions of  the  pipe  were  6  feet  3  inches  long,  and  the 
iron  skeleton  was  formed  by  30  longitudinal  rods,  1-4 
inch  in  diameter,  one  interior  spiral  of  5-32  inch  wire 
and  one  exterior  spiral  of  1-4  inch  wire. 

On  the  2d  of  February,  1901,  16  feet  of  this  conduit 
were  taken  up.  The  tubes  were  found  in  a  perfect 
state  of  preservation ;  the  steel  did  not  show  the  slight- 
est trace  of  oxidation;  the  adhesion  of  the  steel  to  the 
concrete,  despite  the  slight  thickness  of  the  pipes,  was 
such  that  it  could  be  separated  only  by  heavy  blows 
from  a  sledge  hammer. 

SAFETY  OF  ARMORED  CONCRETE  CONSTRUCTION. 

Vested  interests  in  the  old  method  of  buildings  which 
feel  their  existence  threatened  by  the  great  inroads  this 
modern  building  process  makes  into  fields,  formerly 
exclusively  their  own,  are  issuing  at  a  great  expense 
trade  literature,  full  of  exaggerated  accounts  of  failures 
of  armored  concrete  floors,  declaring  reinforced  con- 
crete a  dangerous  novelty,  full  of  uncertainties,  etc. 
Governments  have  investigated  these  questions  and 
have  decided  in  favor  of  reinforced  concrete  construc- 
tion. 

We  see  the  United  States  Government  adopting  rein- 
forced concrete  for  many  important  buildings  of  the 
United  States  Naval  Academy  in  Annapolis,  for  coast 
and  harbor  defence,  and  particularly  for  gun  emplace- 


FIREPROOF  QUALITIES  OF  CONCRETE         127 

ments,  for  cisterns  and  stand-pipes  in  the  different 
forts  on  the  Atlantic  coast,  for  fire-proofing  the  Con- 
gressional Library,  and  the  new  United  States  printing 
office,  etc. 

The  few  failures  which  are  recorded  in  this  country 
can  always  be  traced  to  utter  carelessness  and  utter 
incompetency  on  the  part  of  the  contractor  or  his  em 
ployees.  Reinforced  concrete  is  a  science  like  steel 
construction  and  nobody  can  expect  that  a  contractor 
without  any  engineering  education,  and  whose  only 
knowledge  of  concrete  is  'derived  from  putting  in  con- 
crete footings  or  sidewalks,  is  able  to  design  struc- 
tures in  reinforced  concrete. 

We  find  many  failures  in  steel  and  brick  construction 
due  to  the  same  cause.  We  wish  to  recall  the 
failures  of  two  coliseums  and  the  works  of  the  Western 
Electric  Company  in  Chicago,  etc. 

There  are  to-day  at  least  50x3  million  square  feet  of 
reinforced  concrete  floors  in  use  and  it  is  very  doubtful 
whether  1-2  or  1-3  of  this  area  is  covered  by  tile  floors. 

It  can  not,  therefore,  be  said  that  reinforced  concrete 
is  a  novelty  or  an  experiment.  The  tests  made  in 
this  country  and  in  Europe  have  demonstrated  rein- 
forced concrete  to  be,  in  the  hand  of  the  experienced 
designer,  a  material,  which  can  be  relied  upon  more 
than  the  best  brick,  steel  or  stone  construction. 


CONSTRUCTION     OF     RETAINING     WALLS. 

Reinforced  concrete  retaining  walls  are,  especially 
for  great  heights,  nearly  50  per  cent  cheaper  and  much 
safer  than  solid  concrete  walls.  They  consist,  as  shown 
in  Fig.  90  of  a  base  plate  which  has  a  width  equal  to 
about  5-10  to  8-10  of  the  height  of  the  wall,  a  cur- 
tain wall,  which  varies  in  thickness  from  4  inches  at 
the  top  to  generally  not  more  than  8  inches  at  the 
bottom,  and  vertical  ribs  from  6  feet  to  8  feet  apart, 
connecting  the  curtain  wall  to  the  base  plate  and 
making  the  entire  wall  an  indeformable  structure.  The 
horizontal  earth  pressure  increased  by  the  horizontal 
pressure  from  loads  on  the  ground,  has  the  tendency 
to  slide  the  wall  on  its  base,  and  at  the  same  time,  to 
overturn  it,  which  forces  are  resisted  by  the  weight  of 
the  earth  on  the  base  plate.  It:  is  clear  that  the  curtain 
wall  is  under  bending  stresses  between  the  ribs  from 
the  horizontal  pressure  and  should  be  designed  similar 
to  a  floor  slab;  we  have  noted  the  great  carrying  ca- 
pacity of  reinforced  concrete  slabs,  and,  therefore,  it 
is  perfectly  safe  and  legitimate  to  make  these  curtain 
walls  not  thicker  than  indicated  above,  however  strange 
it  may  appear  on  first  consideration.  The  ribs  with  the 
curtain  walls  form  a  "T"  section,  which  takes  up  the 
bending  moments  from  the  earth  pressure  in  regard 
to  the  wall  as  a  whole.  The  base  plate  is  to  be  designed 
strong  enough  to  sustain  the  weight  of  the  earth  and 
superimposed  loads,  and  the  reaction  of  the  ground. 

128 


RE-INFORCED  CONCRETE  RETAINING  WALLS  129 

We  see  that  every  detail  of  reinforced  concrete  re- 
taining walls  is  capable  of  being  figured  with  certainty 
in  regard  to  the  stresses  which  are  acting  upon  them. 


dl 


f'-H-fl-i-PtH- 

j+THjif-'-J-H 

J-r,TW^: 


Fig.  90. — Reinforced  Concrete  Retaining  Wall. 

We  are  able  to  provide  a  base  which  can  be  given  to 
masonary  walls  only  at  a  ruinous  expense;  besides, 
there  is  no  doubt  that  we  know  more  of  the  nature 
of  stresses  in  reinforced  concrete  than  of  the  distribu- 


130    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

tion  of  stresses  is  a  masonary  wall,  which  is  affected 
by  lateral  forces. 

The  factor  of  safety  against  overturning  reinforced 
'concrete  walls  is  thus  much  greater  than  that  of  re- 


1 

PI*, 

.A3 

\'-'~r-  } 

«'"  •*• 

^ 

.^.*  ^ 

j 

** 

j 

',  •***• 

? 

- 

F 

i 

f  •  • 

i 

i 

t:^\ 

.t  r--  , 

\ 

'A  *  ;  <  ' 

•; 

(.'  #--• 

Fig.  91. — ^Reinforced   Concrete   Retaining   Wall   with   a  plat- 
form at  Mid-height. 

taining  walls  of  any  other  construction,  and  from  an 
engineering  point  of  view  and  from  an  economical 
point  of  view,  there  is  not  the  least  reason  why  these 
walls  should  not  be  adopted  by  railroads  even  for  the 
greatest  heights. 


RE-INFORCED  CONCRETE  RETAINING  WALLS  131 

Fig.  91  shows  a  concrete  retaining  wall  of  a  height 
of  1 6  feet  with  a  platform  at  half  the  height,  which 
arrangement  may  save  in  certain  cases  a  good  deal  of 
excavation. 


CONSTRUCTION      OF      REINFORCED      CON- 
CRETE DAMS. 

These  dams  are  designed  on  similar  lines  to  retaining 
walls.  We  have  again  a  base  plate,  curtain  walls  and 
ribs,  making  the  whole  an  indeformable  structure. 


,   c 
Fig.  92. — Reinforced  Concrete  Dam. 

Figure  92  shows  the  design  of  a  dam  for  a  head  of 
water  of1  about  1 5  feet.  The  curtain  walls  are  inclined 
at  an  angle  of  about  45  degrees  to  a  vertical  line  to 
obtain  as  uniform  a  pressure  on  the  ground  as  possible. 
By  this  arrangement  the  pressure  on  the  ground  is 
the  sum  of  the  weight  of  the  dam  and  the  vertical  com- 
ponent of  the  water  pressure,  which  is  perpendicular 

132 


RE-INFORCED  CONCRETE  DAMS  133 


w  vf 

•  gfc  n  ^.-y  •••••••,-  ~  :•  •  igai^7  ^  ^  -^v  :  ;".-:  —.-) 

'ig.   93.—  Reinfor< 
at  Mid-heigl 

3ed    Concrete   Dam    with 
it. 

bracing    Platform 

- 

Pig.  94. — Section  of  Dam. 


134    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

to  the  curtain  wall,  and  these  two  forces  have  to  pro- 
duce a  friction  sufficiently  large  to  prevent  sliding  of 
the  dam  on  its  base. 

If  there  be  danger  of  sliding,  the  weight  on  the 
ground  can  be  increased  by  filling  the  inside  of  the  dam 
with  earth  up  to  the  line  "ab,"  or  by  providing  a  shoe 


Fig.  £5.— Section  of  Dam   50   feet   high  with  two   Platforms 
built  on  Rock. 

"c,"  or  by  extending  the  base  plate  towards  the  water 
side.  The  water  pressure  will  then  increase  the  fric- 
tion on  the  ground. 

Fig.  93  shows  the  design  of  a  dam  for  a  head  of 
water  from  20  to  30  feet.  It  is  good  practice  as  well 
as  economical  in  this  case  to  introduce  at  one  half  the 


RE-INFORCED  CONCRETE  DAMS 


135 


height  a  platform  connecting  ribs  and  curtain  walls 
which  platform  reduces  the  free,  unsupported  lengths 
of  the  ribs  and  permits  a  reduction  in  the  thickness 
of  the  ribs. 

Fig,   94  shows  the  cross  section  of  this  dam. 

Fig.  95  shows  a  cross  section  of  a  dam  about  50 
feet  in  height,  having  two  platforms  to  stiffen  the  ribs 
and  curtain  walls.  It  is  here  assumed  that  the  dam 
rests  on  rock  and  that  the  base  plate  is  replaced  by 
footings  under  the  ribs  to  distribute  the  weight  on 
the  rock.  The  curtain  walls  are  required  to  withstand 
a  much  greater  pressure  in  clams  than  in  retaining 
walls.  In  a  30  foot  dam  this  presure  at  the  base  is 
1,900  Ibs,  per  square  foot.  It  will  very  rarely  be  neces- 
sary to  make  the  curtain  walls  more  than  12  inches 
thick  at  the  base,  even  under  the  highest  pressure,  be- 


Fig.  96. — Design  for  the  Nile  Dam  at   Assouan,  of  Reinforced 
Concrete,  100  feet  high. 


136    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

cause  the  ribs  are  only  6  to  8  feet  apart.  The  thickness 
of  the  curtain  walls  can  be  reduced  to  4  inches  at  the 
top.  Rich  concrete  should  be  used  for  the  curtain  walL 
and  a  i  inch  to1 2  inch  cement  finish  is  to  be  applied  to 
the  exterior  of  the  wall  to  insure  a  water-proof  curtain. 
Fig.  96  shows  the  design  of  the  Nile  dam  at  Assouan 
for  a  head  of  water  of  100  feet.  This  design  was 
accepted  as  perfectly  reliable  from  an  engineering  point 
of  view,  but  the  difficulty  of  getting  enough  men, 
familiar  with  this  class  of  work,  in  such  an  out-of-the- 
way  place,  was  the  single  reason  that  a  stone  dam  of 
much  greater  cost  was  substituted  for  it. 


TANKS,     STANDPIPES,     CISTERNS,     RESER- 
VOIRS. 

Tanks  and  Standpipes  are  receptacles  for  liquid 
above  ground. 

Cisterns  and  reservoirs  are  partly  or  entirely  in  the 
ground.  Reservoirs  are  large  cisterns.  The  cylind- 
rical form  is  best  adapted  for  these  structures,  produc- 
ing in  the  walls  direct  tensile  stresses,  which  are  taken 
care  of  by  steel  rods,  while  the  concrete  is  assumed  to 
transmit  the  stresses  to  them.  We  have  to  guard 
carefully  against  expansion  cracks  by  imbedding  steel 
rods  also  in  vertical  direction  in  the  walls,  and  in  at 
least,  two  directions  in  the  bottoms.  Where  cisterns 
are  situated  near  rivers,  there  is  sometimes  danger,  that 
by  an  abnormal  rise  of  water  the  cistern  when  only 
partly  full  may  be  lifted  out  of  the  ground  or  the 
bottom  fractured.  In  such  cases  we  have  to  extend  the 
bottom  beyond  the  walls  to  get  the  benefit  of  the 
weight  of  the  surrounding  ground;  and  we  have  also 
to  strengthen  the  bottom  by  girders,  capable  of  with- 
standing the  upward  pressure.  In  tanks  and  cisterns 
the  walls  rarely  need  to  be  made  more  than  6  inches 
thick,  even  for  the  largest  dimensions,  and  often  3 
inches  is  quite  sufficient.  Rich  concrete  has  to  be  used 
to  insure  a  waterproof  job,  which  also  requires  a  ce- 
ment finish  1-2  in.  to  3-4  in.  thick.  This  cement  finish 
should  be  applied  as  soon  as  possible  after  concreting 
sides  and  bottom.  These  surfaces  should  be  carefull) 
cleaned,  and  a  wash  of  cement  applied,  before  spread- 

137 


138    RE-INFORCED  CONCRETE  CONSTRUCTIONS 

ing  the  cement  finish  in  thickness  of  not  more  than 
1-4  in.  at  a  time.  One  hour  or  sd  should  elapse  before 
applying  the  second  coat,  giving  time  to  the  first  coat 
to  get  "fat,"  as  the  workmen  call  it. 


Fig.  97. — 15,000  Gallon  Tank,  at  Bournemouth,  England.  To- 
tal height,  45  feet.  Inside  diameter,  21  feet.  Height 
of  tank  proper,  10  feet. 

Smaller  tanks  and  cisterns  up  to  30  feet  in  diameter 
are  covered  by  domes;  the  larger  sizes  by  ordinary 


RE-INFORCED  CONCRETE  TANKS 


139 


column  girder  and  slab  construction,  as  described  for 
floors  and  roofs.  Groined  arch  coverings  as  often 
used -in  this  country  are  a  simple  waste  of  money  and 


Fig.  98. — 20,000  Gallon  Tower,  Scafati,  Italy. 

cost  at'  least  50  per  cent  more.  It  is  of  course,  possible 
to  make  tanks  and  cisterns,  of  any  other  shape,  as  rec- 
tangular, or  octognal,  etc.  In  this  case  the  sides  of 
the  tanks  are  subjected  to  bending,  and  require  much 
more  steel  than  in  round  tanks.  Cistern  walls  should 


140    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  99—65,000  Gallon  Water  Tanfc  with  Hollow  Walls.  Roof 
covered  with  a  layer  of  earth  one  foot  thick.  Concrete 
housing  for  pipes  and  pump. 


RE-INFORCED  CONCRETE  TANKS 


141 


be  reinforced  on  both  sides,  because  when  the  cistern 
is  empty  the  walls  or  sides  are  acted  upon  by  the  out- 
side, horizontal  earth  pressure,  subjecting  the  inside 


Fig.  100.— 80,000  Gallon   Water  Tanks  used  by  the  Govern- 
ment Railroads  in  France. 

of  the  walls  to  tension,  and  when  the  cistern  is  filled 
with  water  the  water  pressure  will  often  exceed  the 
earth  pressure  subjecting  the  outside  of  the  walls  to 
tension. 


142    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


-  !     \ 


•  //i/ctoa*s*£   eswfjr  7-#/r/r 

Fig.  101.— Section  through  such  a  Tank. 


RE-INFORCED  CONCRETE  TANKS 


Fig.  102.— 3,000,OCO    Gallon    Reservoir  for  the  Watei    Supply  oc 
the  City  of  Lausanne,  Switzerland. 

The  illustrations  show  some  very  artistic  designs 
of  tanks.  They  add  beauty  to  buildings  or  localities 
when  so  erected.  They  are  besides  much  more  dur- 
able than  steel  or  wooden  tanks.  They  do  not  incur 
cost  for  maintenance  and  will  last  for  an  indefinite 
time.  There  are  reinforced  concrete  tanks  used  by 
railroads  in  France,  which  are  over  thirty-five  years 
old. 

Concrete  tanks  can  be  used  for  storing  wine,  mineral 
oils,  tar,  ammoniac,  lyes,  salt-water,  etc. 


144    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


o 
o 
o 

t 
I 


GRAIN  ELEVATORS,  COAL    AND    ORE    BINS, 
LIME  AND  SALT  BINS. 

These  structures  are  designed  and  constructed  on 
lines  similar  to  tanks.  The  circular  form  is  here  also 
the  most  economical  arrangement ;  it  is,  however,  often 
desirable  to  build  elevators  and  bins  in  clusters,  and 
in  this  case,  square,  rectangular,  or  hexagonal  bins  are 
preferable  to  round  bins.  Round  bins  built  in  clusters 
leave  a  nearly  triangular  space  between  them,  which 
is  practically  lost;  where  these  spaces  are  filled  with 
grain  great  bending  moments  in  the  adjoining  cylin- 
ders are  produced,  which  sometimes  caused  failure  of 
the  structure.  The  horizontal  pressure  from  grain  or 
coal  is  considerably  less  than  water  pressure,  and  ex- 
perience proves,  if  a  certain  height  of  bin  is  exceeded, 
this  pressure  is  nearly  constant  on  the  sides  of  the 
bin  below  this  certain  height.  The  sides  of  rectangu- 
lar bins  if  arranged  in  clusters,  must  be  reinforced  on 
both  faces,  because  one  bin  may  be  filled  and  the  ad- 
joining empty  and  vica  versa.  The  bottoms  of  the 
bins  are  generally  suspended  from  the  sides ;  they  sup- 

145 


146    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED   CONCRETE  BINS 


147 


•4- 


i 

01 

L 


148    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED   CONCRETE  BINS 


149 


150    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED   CONCRETE  BINS  151 

port  a  relatively  small  part  of  the  weight  of  the  ma- 
terial in  a  bin,  especially,  when  the  height  of  material 
is  a  multiple  of  the  width.  A  man  can  easily  inter 
rupt  the  stream  of  grain  out  of  a  six  inch  hole  at  the 
bottom  with  his  hands,  even  in  the  case  of  high  bins, 
while  in  a  tank  the  pressure  at  a  six  inch  opening 
would  be  very  great. 

The  thickness  of  sides  and  bottoms  rarely  exceeds 
six  inches,  if  stiffened  by  horizontal  girders  at  proper 
intervals.  The  bins  are  generally  supported  by  col- 
umns at  the  intersection  of  two  side  walls;  and  as 
the  bins  are  very  often  built  near  rivers  or  harbors, 
where  foundations  are  very  bad,  a  raft  over  the  whole 
area  is  generally  applied. 

Figs.  104  and  105  show  a  grain  elevator  at  Swan- 
sea, England  with  bins,  five  feet  by  ten  feet  and  sixty- 
six  feet  high.  Fig.  106  shows  a  one  million  bushel 
grain  elevator,  in  Genoa,  Italy,  with  bins  10x14  feet 
and  57  feet  high. 

Figs.  107  and  108  show  a  grain  elevator  at  Dun- 
ston-on-Tyne,  England,  with  bins  14x14  feet,  and  60 
feet  high. 

Reinforced  concrete  grain  elevators  have  been  used 
in  Europe  for  more  than  20  years.  They  give  perfect 
satisfaction,  do  not  cause  sweating,  and  are  the  only 
type  of  fire-proof  elevators  known  there. 

Fig.  no  shows  a  coal  bin  at  Lens,  Belgium.  One  of 
the  columns  was  knocked  off  by  a  derailed  loco- 
motive, and  though  the  bins  were  filled,  the  sides 
were  strong  enough  to  hold  up  the  tremendous  weight 
without  cracking. 

Fig.  in  shows  a  coal  bin  of  considerable  height. 
No  damage  to  the  sides  or  bottom  is  experienced  by 


152    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  109.— Coal  Bins,  Foot  Bridge  and  Factory  of  Reinforced 
Concrete.  The  bottom  of  the  bin  is  28  feet  above  the 
ground.  < 


RE-INFORCED   CONCRETE  BINS 


153 


154    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  110.— Coal  Bins. 

the  dropping  of  a  ton  of  coal  at  a  time  through  the 
opening  at  the  top. 

Fig.  112  shows  a  storage  bin,  without  any  inside 
partitions,  built  by  the  Hecla  Portland  Cenrent  Co.,  at 
their  works  at  Edwards  Lake,  Mich. 

This  class  of  reinforced  concrete  structures  i» 
considerably  cheaper  than  steel  construction,  and  un- 
doubtedly will  have  a  great  future,  also  in  this  coun- 
try once  their  great  advantages  in  regard  to  strength, 
durability  and  fireproof  qualities  are  fully  understood. 


RE-INFORCED   CONCRETE  BINS 


155 


Kig.  112. — Storage  Bins,  Hecla  Portland  Cement  Co. 


Fig.  113. — Detail  of  Splicing  Reinforcing  Rods 
for  Tanks  and  Water  pipes. 


REINFORCED     CONCRETE     WATER     PIPES, 
SEWERS  AND  CULVERTS. 

This  branch  of  reinforced  concrete  construction  be- 
longs to  the  oldest  application  of  armored  concrete. 

Water  mains  are  built  from  6  inches  up  to  more  than 
200  inches  in  diameter,  and  the  thickness  of  the  con- 
crete shell  is  rarely  made  less  than  i  1-4  inches,  nor 
more  than  4  inches.  The  material  used  is  rich  cement 
mortar  in  the  proportion  of  not  less  than  i  part  cement 
to  3  parts  sand. 

All  tensile  stresses  arising  from  interior  pressure 
are  taken  care  of  by  steel  rods,  which  are  placed  closely 
together  in  both  circumferential  and  longitudinal  di- 
rections, so  that  the  cement  mortar  acts  only  as  a 
filling  to  transmit  the  stresses  to  the  steel  rods  and 
to  make  the  pipes  water-tight. 

It  is  good  practice  to  introduce  at  intervals  of  from 
150  to  200  feet  a  sliding  joint  on  account  of  expansion 
and  contraction  due  to  changes  of  temperature,  simi- 
lar to  the  expansion  joints  used  in  cast  iron  pipes. 

During  the  first  week,  after  water  has  been  turned 
on,  more  or  less  seepage  takes  place  due  to  the  slight 
porosity  of  the  cement  mortar,  which  decreases  very 
rapidly  by  the  pores  gradually  being  filled  up  by  the 
sediment  in  the  water  as  it  passes  through  the  shell, 
and  it  is  not  perceptible  after  a  period  of  about  three 
months,  where  the  head  of  water  is  less  than  50  to 
70  feet.  For  higher  pressures  water-tightness  should 

156 


RE-INFORCED   CONCRETE   PIPES 


158    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


RE-INFORCED   CONCRETE  PIPES 


159 


be  secured  by  thin  sheet  steel  tubes  about  1-16  of  an 
inch  thick,  which  shell  for  pressures  of  250  feet  and 
more  is  to  be  increased  in  thickness  to  1-8  or  1-4  of 
an  inch. 

The  smaller  pipes  are  manufactured  in  a  factory 
or  in  movable  works,  near  the  place  where  they  are 
to  be  used,  in  lengths  from  3  to  15  feet,  and  have 
either  hub  and  flat  eend  connction  as  shown  in  Fig. 
1 14,  or  sleeve  connections,  as  shown  in  Fig.  115. 


Fig.  118. — Manufacture  of  Pipes  in  Movable  Works. 

The  water-tight  joint  is  made  by  pouring  rich  ce- 
met  mortar  into  the  space  between  the  pipe  and  the  hub 
or  the  sleeve. 


160    RE-INFORCED  CONCRETE  CONSTRUCTIONS 


Fig.  121. — Pipe  of  5  feet  9  inches  diameter.     Paris  Sewage 
Disposal  System. 


Fig.  122. — Manufacture  of  Reinforced  Skeletons. 


RE-INFORCED   CONCRETE   PIPES 


1G1 


162     RE-INFORCED    CONCRETE    CONSTRUCTIONS 

Larger  pipes  are  built  up  in  the  trench  by  the  aid 
of  movable  centerings,  making  the  whole  pipe  line  one 
monolith. 

There  is  very  little  danger  of  the  sheet  steel  lining 
corroding,  because  the  enclosed  air  is  under  high 
pressure  and  does  not  attack  the  steel.  In  some  cases 
it  might  be  advisable  to  protect  the  inside  of  the  lin- 
ing by  an  inner  reinforced  concrete  pipe. 

Fig.  117  to  123  show  the  manufacture  of  rein- 
forced concrete  pipes  of  medium  diameters. 


Fig.  124. — Reinforced  Concrete  Flume  on  Reinforced  Concrete 
Trestle  conveying  the  Water  of  the  River  Rhone  to  the 
new  Simplon  Tunnel. 

Fig.-  124  to  126  show  a  flume  built  of  reinforced 
concrete  to  supply  water  from  the  River  Rhone  to  the 
2,000  H.  P.  turbines  at  the  mouth)  of  the  new  Simplon 
tunnel.  It  has  a  square  section,  6  feet  4  inches  inside, 
the  walls  being  4  inches  thick.  It  is  9,800  feet  long 
and  runs  partly  in  the  ground  and  partly  on  a  rein- 


RE-INFORCED   CONCRETE   PIPES 


103 


164    RE-INFORCED    CONCRETE   CONSTRUCTIONS 

forced  concrete  trestles,  in  some  places  30  feet  high, 
and  it  also  crosses  two  streets  on  canal  bridges  of  35 
feet  span. 

The  cost  of  a  wooden  flume  would  have  been  85 
francs  per  lineal  meter,  while  the  reinforced  concrete 
flume  was  built  for  100  francs  per  meter.  Considering 
that  the  water  power  is  to  be  a  permanent  feature  of  the 
tunnel  to  supply  electrical  power  required  for  moving 
the  trains  through  the  tunnel,  it  is  clear  that  reinforced 
concrete  in  this  case  was  the  most  economical  form 
of  construction. 


Fig.  127.— Power  Canal  and  Spillway. 


RE-INFORCED    CONCRETE   SEWERS 
REINFORCED  CONCRETE  SEWERS. 


165 


Reinforced  concrete  sewers  are  built  on  lines  sim- 
ilar to  water  mains.  The  most  favorable  section  in 
this  case  is  not  a  round,  but  a  parabolic  shape.  The 
steel  reinforcement  is  not  required  to  be  as  high  as  in 


Fig.  128. — Section  through  Tunnel  17  feet  wide,  and  Rein- 
forced Concrete  Sewer  for  Sewage  Disposal  System  of 
the  City  of  Paris. 

water  mains.  There  is  little  danger  of  a  sewer  being 
injured  by  super-imposed  loads,  as  a  parabolic  arch 
of  a  thickness  of  only  3  to  4  inches  has  an  enormous 
carrying  capacity,  as  shown,  for  example,  in  Fig.  128, 
representing  a  17  feet  tunnel  covered  by  17  feet  of 
earth,  which  \vas  built  of  a  shell  of  armored  concrete 
less  than  3  inches  thick,  and  was  tested  by  a  movable 
load  of  ii  tons  without  any  sign  of  weakness,  deflect- 
ing under  this  concentrated  load  not  more  than  1-25 
of  an  inch. 


1GG     RE-INFORCED    CONCRETE    CONSTRUCTIONS 

Filling  of  the  trench  on  one  side  only  will  be  a 
source  of  great  danger  to  the  concrete  shell,  if  this 
unsymmetrical  load  has  not  been  provided  for  in  the 
original  design. 


Fig.  129. — Sewer  Sections  of  small  Diameters. 

Inasmuch  as  the  greatest  portion  of  the  weight  of 
the  earth  is  above  the  crown  of  the  sewer,  the  designer 
is  liable  to  fall  into  the  error  of  not  duly  providing  for 
the  strains  to  which  the  sewer  is  subjected  during  the 
filling  of  the  trench.  It  is  apparent  that  the  invert  of 
the  sewer  must  be  amply  reinforced  to  withstand  the 
upward  pressure  of  the  ground,  due  to  the  weight  of 
the  sewer  and  the  super-imposed  loads. 

There  are  many  sewers  built  in  the  United  States 
of  diameters  of  10  to  15  feet,  having  a  thickness  at 
the  crown  of  i  1-2  to  2  feet.  This  is  often  an  extrava- 
gant waste  of  money  and  material. 


RE-1NFORCED    CONCRETE   SEWERS          167 

Where  sewers  must  be  built  on  treacherous  soil  it 
may  be  of  advantage  to  drive  piles  every  10  feet,  and 
to  make  the  shell  of  the  sewer  to  act  as  a  girder  be- 
tween the  piles,  able  to  carry  itself,  its  contents,  and 
the  super-imposed  loads. 

Nearly  all  of  the  cities  in  Europe  have  abandoned 
brick  sewer  construction,  and  substituted  reinforced 
concrete. 


.5-Scm      - 


Fig.  130. — German    Sewer    Sections,    of   Reinforced   Concrete 
Construction. 

Fig..  130  shows  a  section  of  a  sewer  as  it  is  adopted 
in  most  cities  in  Germany. 

The  City  of  Paris  in  the  construction  of  its  sewage 
disposal  system  adopted  reinforced  concrete  exclusively 
and  has  about  17  miles  of  conduits  up  to  10  feet  in 
diameter,  in  successful  operation.  See  Figs.  121  to 
123. 

Large  factories  exist  all  over  Europe,  producing 
pipes  and  conduits  of  various  shapes,  sizes  and  di- 
ameters, notably  the  Dykerhoff  &  Widemann  factories, 
which  employed  in  1900  two  thousand  five  hundred 
men. 

Fig.  131  is  a  view  of  one  of  these  factories.  . 


168     RE-INFORCED    CONCRETE   CONSTRUCTIONS 


RE-INFORCED   CONCRETE   SEWERS  169 

REINFORCED    CONCRETE    CULVERTS. 

American  railways  are  improving  their  right  of 
way  by  permanent  concrete  culverts,  and  while  they 
used  up  to  a  very  recent  date  only  massive  concrete 
construction,  they  are  now  beginning  to  appreciate  the 
great  economical  advantages  of  a  well  designed  rein- 
forced concrete  culvert.  The  most  economical  form  is 
of  a  parabolic  section  and  almost  any  thickness  of  shell 
will  be  capable  of  supporting  the  heaviest  super-im 
posed  loads  provided  that  'due  precautions  are  taken 
to  avoid  eccentric  stresses  during  the  process  of  filling 
the  earth  around  it. 

Where  the  high  parabolic  section  is  not  exactly  suit- 
able, a  culvert,  consisting  of  vertical  side-walls  and 
of  a  parabolic  or  flat  covering,  may  be  substituted. 

The  side-walls  must  be  figured  for  the  lateral  earth 
pressure  as  well  as  for  the  horizontal  pressure  due  to 
the  live  train  loads  on  similar  lines  as  described  for 
basement  and  retaining  walls.  The  flat  cover  may  be 
a  reinforced  concrete  slab  for  spans  less  than  ten  feet 
or  of  girder  and  slab  construction  for  larger  spans. 


MISCELLANEOUS  APPLICATIONS. 

To  enumerate  or  even  specialize  the  almost  universal 
application  of  reinforced  concrete  is  a  task  far  beyond 
the  scope  of  this  handbook. 

Therefore  we  will  describe  only  a  few  of  the  most 
important  uses. 

REINFORCED  CONCRETE  SMOKE  STACKS. 

Many  reinforced  concrete  smoke  stacks  have  been 
built  in  this  country  and  Europe  during  the  past  15 
years.  These  stacks  are  much  stronger  than  solid  or 
hollow  brick  chimneys,  and  can  be  erected,  not  only 
in  a  much  shorter  time,  but  also  at  very  great  reduction 
in  cost. 

Figs.  132  and  133  show  a  concrete  chimney  erected 
by  Mr.  C.  Leonardt,  Los  Angeles,  California,  for  the 
Los  Angeles  Electric  Railway  Power  S  cation.  It  has 
an  inside  diameter  of  n  feet  and  is  155  feet  high  above 
grade.  It  consists  of  solid  concrete  masonry  up  to 
36  feet  above  the  ground ;  from  there  up  of  an  outside 
and  an  inside  shell  of  reinforced  concrete,  which  latter 
can  expand  independent  of  the  outside  wall. 

Fig.  134  shows  the  movable  mold  used  for  con- 
creting the  shells. 

In  Fig.  78  is  shown  a  chimney  130  feet  high  buih 
of  a  solid  shell  of  reinforced  concrete. 

Fig.  135  shows  a  lime  kiln  built  of  a  shell  of  rein- 
forced concrete  lined  with  fire  brick,  which  stood  for 

170 


MISCELLANEOUS  APPLICATIONS 


Fig.    132.— Reirforced    Concrete    Chimney,    in  course   of  erec- 
tion, Los  Angeles. 


172     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


fig.  133. — Completed  Chimney  for  Los  Angeles  Power  Co. 


/ 

I  UNivens 

MISCELLANEOUS  APPLICATIONS 


17:5 


Fig.  134. — Movable  Centerings  for  this  Chimney. 


174     RE-INFORCED    CONCRETE   CONSTRUCTIONS 


MISCELLANEOUS  APPLICATIONS 


175 


176     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  136b.— Dome  of  40  feet  diameter.     Bank  Brunner,  Brus- 
sels, Belgium. 

years  has  withstood  temperatures  of  2,000  to  2,200  de 
grees  Fahrenheit. 

Fig.  136  shows  reinforced  concrete  domes  of  dar- 
ing design.  There  is  no  material  which  is  better 
adapted  for  this  class  of  structures  than  reinforced 
concrete.  Even  for  the  largest  diameters  a  thickness 


MISCELLANEOUS  APPLICATIONS  IT? 


Fig.  137. — Printing  Establishment,   Rennes,   France.     Arches 
of  80  feet  span. 

of  three  inches  at  the  crown  and  five  to  six  inches  at 
the  springing  is  quite  sufficient. 

Fig.  137  shows  a  hall  for  a  printing  establish- 
ment at  Rennes,  France,  consisting  of  concrete  arches 
of  8 1  feet  span,  concrete  purlins  and  a  concrete  roof 
with  skylights.  Reinforced  concrete  arches  can  be 
built  at  very  reasonable  expense  up  to  200  feet  in  span 
and  over  for  railroad  stations,  public  halls,  factories, 
etc.,  and  possess  many  advantages  over  steel  arches. 
They  are  fireproof  and  indestructible,  cost  much  less, 
can  be  maintained  at  very  little  expense,  have  a  fine 
architectural  appearance  and  afford  better  light  for  the 
interiors. 

Fig.  138  shows  a  railroad  tower  built  of  reinforced 
concrete.  The  French  railroads  build  small  guard 


178     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  138. — Railroad  Guard  Tower  used  by  French  Railroads 
Foundations  are  .enlarged  for  greater  stability. 


MISCELLANEOUS  APPLICATIONS  179 

houses  of  reinforced  concrete  and  ship  them  com- 
pletely finished  on  cars  to  the  places  where  they  are  to 
be  used. 


Fig.  139. — Reinforced    concrete    side-walk      lights,      Power 
Building,  Cincinnati,  built  by  the  Ferro-Concrete  Con- 
struction Co.    Cincinnati. 

Figs.  139  and  140  show  prismatic  sidewalk  lights 
with  reinforced  concrete  framing.  The  glass  inserts 
are  two  and  three-fourths  inches  in  diameter  and  three 
and  three-fourths  inches  on  centers,  while  the  concrete 
frame  is  one  and  three-fourths  inches  thick,  strength- 
ened by  small  steel  rods  in  both  directions.  Nearly 
all  the  subway  stations  of  the  New  York  Rapid  Transit 
Railway  have  reinforced  concrete  sidewalk  lights. 

Leading  American  railways  are  now  experimenting 
with  reinforced  concrete  ties,  with  a  view  of  displacing 


180     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  14i>.— View  of  Reinforced  Concrete  Side-walk  Lights  from 
below. 


MISCELLANEOUS  APPLICATIONS  181 

the  ordinary  wooden  ties  which  are  yearly  becoming 
more  expensive. 

The  .Italian  government,  after  experimenting  several 
years  with  reinforced  concrete  ties,  has  adopted  a  stand  • 
ard  concrete  tie  on  all  the  government  railways. 

The  French  railroads  in  China  on  their  right-of-way 
of  over  300  miles,  use  reinforced  concrete  ties  ex- 
clusively, having  an  inverted  "T"  section,  with  an  en- 
largement of  the  stem,  where  the  rails  cross,  which  ties 
cost  about  two  and  a  half  dollars  each. 

These  ties  are  much  more '  expensive,  in  the  first  in- 
stance. Their  greater  life,  however,  after  10  years' 
use,  will  result  in  decided  saving. 

Reinforced  concrete  fence  posts  are  rapidly  coming 
into  use  in  the  United  States,  by  railroads  along  their 
right-of-way,  especially,  in  prairie  countries  where  fire 
hazards  are  great.  Statistics  show  that  60  per  cent,  of 
the  fence  posts  of  the  right  of  way  are  destroyed  by 
fire  against  40  per  cent,  by  decay. 

Reinforced  concrete  is  likewise  coming  into  extensive 
use  for   agricultural   purposes,   as,    for  example,    for 
small  water  and  feed  tanks,  silos,  for  irrigation  ditches 
etc. 


REINFORCED  CONCRETE  BRIDGES. 

Reinforced  concrete  combining-  the  massive  effect 
of  brick  and  stone  and  the  great  strength  of  steel  has 
found  a  great  field  of  application  in  bridge  building. 

The  rapid  progress  accomplished  in  bridge  con- 
struction during  the  last  30  years  is  due  to  the  use 
of  steel,  which,  being  of  relatively  small  weight,  en- 
abled engineers  to  erect  large  spans  without  the  use 
of  costly  scaffolding.  Both  iron  and  steel  are  liable  to 
deterioration  by  rust,  and  as  some  parts  cannot  easily 
be  inspected  or  painted,  the  life  of  a  steel  bridge  is 
very  limited,  and  steel  bridges  are  to-day  considered  as 
temporary  structures. 

Consequently  the  first  class  railways  in  this  country 
are  again  returning  to  stone  or  solid  concrete  bridges 
which  offer  the  advantage  of  great  stiffness  and  dura- 
bility. 

The  use  of  steel  reduced  the  cost  of  bridges  to  a 
considerable  extent ;  engineers  continually  increased  the 
working  stresses  to  be  allowed  in  the  calculation  of  thj 
bridge  members,  and  the  result  is  light  bridges,  which 
are  liable  to  be  wrecked  in  a  short  time  by  the  con- 
tinuous traffic  of  ever  increasing  loads.  Reinforced 
concrete  bridges  can  be  expected  to  last  for  ever ;  just 
as  the  old  Roman  concrete  walls  outlasted  their  stone 
linings,  even  so  can  we  expect  concrete  bridges  to 
outlast  stone  bridges.  Repairs  and  cost  of  maintenance 
are  reduced  to  a  minimum ;  they  can  be  built  at  a  rea- 
sonable cost,  very  often  for  less  money  than  steel 

182 


RE-INFORCED  CONCRETE  BRIDGES  183 

bridges;  they  are  10  to  20  times  more  rigid  than  the 
latter. 

The  first  application  of  reinforced  concrete  in  bridge 
construction  was  in  concrete  floors  of  steel  bridges, 
especially  in  city  bridges  where  a  permanent  floor  was 
required. 

The  usual  distance  of  stringers  in  steel  bridges  is  3 
to  5  feet,  and  it  is  perfectly  feasible  to  cover  them  by 
a  concrete  floor  i  1-2  to  2  inches  thick,  capable  of  sup- 
porting any  concentrated  or  distributed  load,  which 
may  come  on  the  bridge.  Reinforced  concrete  now 
replaces  the  very  expensive  floorings,  which  were  N for- 
merly made  of  buckle  plates,  suspension  plates,  or 
various  kinds  of  trough  floors  with  a  covering  of 
concrete. 

These  concrete  floors  are  not  only  more  durable 
but  also  much  lighter,  saving  a  great  amount  of  dead 
weight  and,  therefore,  steel  in  the  bridge  and  costing 
less  than  the  old  floorings. 

The  next  application  of  reinforced  concrete  in 
bridges  was  due  to  the  demand  of  railroads  for  viaducts 
of  very  limited  depth  for  street  and  railroad  crossings. 
For  railroad  crossings  it  was  possible  to  span  distances 
up  to  20  feet  by  a  reinforced  concrete  slab,  only  six 
inches  thick,  while  for  street  crossings  a  thickness  of 
12  inches  for  a  span  of  10  feet  has  proved  very  satis- 
factory. 

Fig.  141  shows  a  cross  section  of  such  a  flat  bridge 
of  10  feet  span,  carrying  a  railroad  track  of  the  Jura 


: •  *..<  *.».*.  r  .....*..*  .  »  « 

-t 

Fig..  141. — Railroad   Bridge   of   10   ft.    span,   Reinforced   Slab 
Construction. 


184     RE-INFORCED    CONCRETE   CONSTRUCTIONS 


Fig.  142. — Reinforced  Concrete  Girder  Railroad  Bridge. 


Fig.  143.— Girder  Bridge  of  50  ft.  span. 


RE-INFORCED  CONCRETE  BRIDGES 


185 


Simplon  R.  R.  Greater  spans  than  10  feet  for  rail- 
road bridges  should  be  of  girder  and  slab  construction. 
Fig.  142  shows  the  first  viaduct  of  this  kind,  built 
at  Creux  du  Mas,  Switzerland.  It  consists  of  10x12 
inch  beams,  six  feet  apart,  spanning  21  feet  4  inches, 
on  a  skew  of  24  degrees.  Tests  made  by  the  Rail- 
road Co.  before  acceptance  of  this  structure  showed 
deflections  of  0.13  inch,  when  the  heaviest  locomotive 
passed  at  a  speed  of  40  miles  an  hour.  Tests  made 
two  years  later  showed  that  this  deflection  had  dimin- 
ished 1-3,  proving,  without  doubt,  that  the  adhesion 
of  plain  round  steel  rods  to  concrete  is  sufficient  and 
not  weakened  by  vibrations  caused  by  passing  trains 
and  that  a  reinforced  concrete  bridge  becomes  stronger 
with  age. 


Fig.  144. — Girder  Bridge  tested   by  a  20   ton   Steam   Roller. 
Maximum  deflection  1-12,000  of  the  span. 


186     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  145.— Reinforced  Concrete  Girder  Bridge  of  52  ft.  span.i 
Rubblestone  abutments,  girders  slightly  arched. 

A  very  economical  type  of  highway  bridges  is  shown 
by  Figs.  143  to  145.  Reinforced  concrete  girders, 
six  to  fourteen  feet  apart,  support  the  roadway,  con- 
sisting of  a  concrete  slab,  stiffened  by  girders,  while 
the  side-walks  are  built  in  cantilever,  as  shown  in 
Fig.  146.  The  roadway  can  be  formed  of  macadam  or 


Fig.  146.— Section  through  Reinforced  Girder  Bridge. 


RE-INFORCED  CONCRETE  BRIDGES  187 


Fig.  147. — Bridge  at  Fort  De  Bron,  designed  to  carry  a  load 
of  extremely  heavy  pieces  of  artillery  for  the  fort. 


Fig.  148. — Continuous  Girder,  Bridge  on  Concrete  Pier  Foun- 
dation. 


188     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

of  a  layer  of  asphalt  or  of  a  two  inch  cement  finish 
The  abutments  for  such  bridges  can  be  built  of  rubble 
stone  or  reinforced   concrete  or  concrete   sheet  piles 
where  the  ground  is  very  bad  and  a  low  priced  bridg 
is  desired. 

These  bridges  are  very  rigid  and  the  tests  on  above 
bridges  of  50  feet  span  showed  under  a  moving  load 
of  twenty  tons  a  maximum  deflection  of  1-12,000  of 
the  span. 

Fig.  147  shows  a  continuous  girder  bridge  with 
reinforced  concrete  trestle  supports,  while  Fig.  148 
shows  a  continuous  girder  bridge  on  concrete  piers  of 
small  diameters,'  which  piers  reduce  as  little  as  possible 
the  profile  of  the  river.  This  class  of  bridges  can  be 
built  with  advantage  for  unsupported  spans  up  to  70 


Fig.  149. — Tubular  Bridge  connecting  two  Refrigerators. 


RE-INFORCED  CONCRETE  BRIDGES 


189 


feet ;  for  larger  spans  they  become  more  expensive  than 
arched  bridges.  Fig.  149  shows  a  tubular  bridge  con- 
necting two  refrigerating  plants  of  a  brewery. 

Arched  bridges  of  reinforced  concrete  can  be  built 
up  to  500  feet  span.  The  great  success  of  armored  con 
crete  in  building  arched  bridges  is  based  on  the  adop- 
tion of  arched  ribs  similar  to  steel  bridges  and  by 
supporting  the  roadway  by  columns  resting  on  the 
arched  ribs.  This  reduces  the  dead  weight  and  the 
cost  of  the  bridge.  Other  systems  of  reinforced  con- 
crete construction  usually  adopt  an  arched  floor  6 
inches  to  3  feet  thick  with  spandrel  walls,  filling  in  the 
space  between  arches  and  the  road  grade  with  earth, 
and  paving  the  surface.  This,  of  course,'  gives  a  much 


Fig.  150. — Covering  of  a  Subway  of  the  Metropolitan  Electric 
Railway,  Paris,  France.  Girders,  52  ft.  span;  live  load, 
200  pounds  per  square  foot. 


190     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

heavier  bridge,  similar  to  a  solid  stone  bridge,  and  con- 
siderably increases  the  weight  on  the  foundations  and 
arched  floors.  Reinforced  concrete  should  not  imitate 
stone,  but  should  create  its  own  particular  style  of 
architecture,  which  is  light  and  graceful ;  in  case  of 
arched  bridges  this  approaches  more  the  design  of  steel 
bridges  than  stone  bridges.  Fig.  [51  shows  a  splen- 
did example  of  an  arched  concrete  bridge.  It  was 
built  in  1898,  at  Chaterellault,  France,  and  is  26  feet 
wide  by  450  feet  long.  The  central  arch  has  a  spaii 
of  164  feet  and  the  side  arches  of  135  feet.  All  arches 
haye  a  rise  of  i-io  of  the  span.  There  are  4  concrete 
ribs  6  feet  3  inches  apart,  being  only  20  inches  deep  in 
the  centre,  which  are  connected  throughout  by  a  five 
inch  concrete  floor  for  wind  bracing.  The  road  bed 
consists  of  a  concrete  floor  5  inches  thick  at  the  curb 
and  10  inches  thick  at  the  centre,  which  is  covered  by 
a  coat  of  asphalt  and  supported  by  girders  6  feet 
3  inches  apart  corresponding  to  the  arches  below,  which 
girders  are  carried  by  8  inch  square  colums,  rest- 
ing on  the  ribs.  The  piers  are  built  of  a  shell  of  con- 
crete 4  inches  to  12  inches  thick,  connected  by  partitions 
in  the  same  vertical  plan  as  the  arched  ribs  and  the 
whole  is  filled  with  a  low  grade  concrete.  The  piers 
rest  on  the  rock  which  was  found  at  a  small  depth 
below  the  river  bottom.  The  side-walks,  which  are 
5  feet  wide,  overhang  for  a  distance  of  3  feet  5  inches. 
The  bridge  was  built  in  the  short  time  of  3  months, 
and  cost  slightly  less  than  $35,000. 

The  tests  by  a  Commission  of  Engineers  and  repre- 
sentatives of  the  government  and  the  municipality  of 
Chatellerault  were  made  in  the  following  manner : 

First,  each  span  was  loaded  over  its  total  length,  then 
on  each  half,  then  on  its  central  part,  with  moist  sand 


RE-INFORCED  CONCRETE  BRIDGES 


191 


Fig.  151.— Bridge  at  Chatellerault,  26  feet  by  450  feet  long, 
central  arch  of  4^9  ft.  span,  side  arches  135  ft.  span, 
rise  1-10  of  the  span. 


Fig.  152.— Bridge  at  Chatellerault 


192     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  153.— Bridge  at  Chatellerault  with  soldiers  passing  over. 

B 

1,50  2.5P  2.50  1,50 


Fig.  154. — Section  through  Pier  of  Chatellerault  Bridge. 


RE-INFORCED  CONCRETE  BRIDGES 


193 


194     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  156. — Highway  and  Electric  Railway  Bridge  at  Bilbao, 
Spain.  Consists  of  five  arches,  of  120  ft.  span,  of  which 
only  three  are  visible  in  the  illustration.  This  bridge 
has  a  much  lighter  appearance  than  a  steel  bridge. 

at  the  rate  of  165  pounds  per  square  foot  on  the  road- 
way and  123  pounds  on  the  side- walks. 

The  official  report  of  the  test  is  as  follows  : 

The  maximums  of  deflections  weree  1-4  inch  for  the 
arch  at  the  left  bank,  7-32  inch  for  the.  arch  at  the 
right  bank,  and  13-32  inch  for  the  central  arch,  that  is 
1-7300  and  1-5000  of  the  spans,  respectively.  The 
specifications  allow  deflections  of  9-16  inch  for  the 
135-foot  span  and  2  inches  for  the  1 64-foot  span. 
After  removing  the  loads  no  permanent  deflection 
could  be  detected. 

The  moving  test  load  consisted  of  \ 

First.     One  1 6-ton  steam  roller. 


RE-INFORCED  CONCRETE  BRIDGES 


195 


Fig.  157. — Cantilevers  of  27  feet  carrying  a  Railroad  track. 

Second.  Two  four-wheeled  wagons  weighing  16 
tons  in  all. 

Third.  Six  two-wheeled  wagons  weighing  8  tons  in 
all;  making  a  total  of  forty  tons  moving  simultane- 
ously over  the  bridge,  while  the  sidewalks  were  loaded 
to  80  pounds  per  square  foot.  Strips  of  wood  were 
strewn  over  the  roadway  in  order  to  produce  shocks 
when  the  steam  roller  passed  over  them.  The  maxi- 
mum deflection  under  these  loads  was  less  than  1-9000 
of  the  span. 

Furthermore,  a  troop  of  250  infantrymen  crossed -the 
bridge,  first  in  ordinary  marching  order,  then  in  double 
quick  time. 

The  most  remarkable  feature  shown  by  these  tests 
was  that  a  load  on  one  arch  caused  a  perceptible  rise 
in  the  two  adjacent  arches,  an  evident  proof  that  ferro- 
concrete structures  are  monoliths. 


196     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  158. — Arched  Bridge  of  60  ft.  span.  Ribs  support  by 
means  of  spandrel  columns,  the  reinforced  concrete 
roadwiay;  railings  consist  of  reinforced  concrete  posts 
and  arches. 


Fig.  159. — Arched  Bridge  of  50  ft.  span. 


RE-INFORCED  CONCRETE  BRIDGES  197 

Figs.  158  and  159  show  smaller  arched  bridges  de- 
signed on  similar  lines  with  the  difference,  that  the 
arched  ribs  are  not  connected  by  a  concrete  floor  for 
wind  bracing,  but  only  by  8x8  inch  ties.  In  this  case 
the  wind  stresses  must,  of  course,  be  taken  care  of  by 
the  concrete  floor  of  the  roadway  and  transmitted  from 
the  arched  ribs  by  the  spandrel  columns  to  this  road- 
way. This  makes  a  very  neat  and  low  priced  design, 
and  bridges  of  this  type  will  be  found  to  be  less  ex- 
pensive than  steel  bridges  with  wooden  floors. 


Fig.  160. — 'Arched   Bridge  carrying  a   canal. 

Figs.  1 60  to  167  show  arched  bridges  where  the  ribs 
are  solid  from  the  roadway  down.  This  is  in  imita- 
tion of  arched  stone  bridges,  the  difference  being  that 
these  bridges  consist  of  ribs  from  6  to  10  feet  apart 
with  a  concrete  floor  for  the  roadway  and  therefore  of 


198     RE-INFORCED    CONCRETE   CONSTRUCTIONS 


Fig.  161. — Foot  Bridge  over  Railroad,  60  ft.  span. 

hollow  construction  and  much  lighter  than  stone 
bridges,  while  they  resemble  them  in  appearance.  Fig. 
1 60  shows  a  concrete  bridge  carrying  a  conduit;  con- 
sists of  two  arches  each  of  42  feet  span,  and  a  cantilever 
sidewalk.  .  Figs.  161  and  162  show  veary  neat  de- 
signs for  foot  bridges  over  railroad  tracks.  The  cost 
of  these  bridges  was  about  25  per  cent,  less  than  of 
structural  steel.  Fig.  168  shows  an  arched  bridg- 
designed  on  the  Monier  system  with  an  arched  floor 
and  concrete  walls  to  support  the  roadway. 


RE-INFORCED  CONCRETE  BRIDGES  199 


Fig.  162. — Foot  Bridge  of  100  ft.  span. 


Fig.  163. — Reinforced  Arched  Highway  Bridge  of  50  ft.  span. 


200     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


Fig.  164.— Highway  Bridge  with  Stone  Lining. 


Fig.  165.^Skew  Bridge  of  72  ft.  span. 


RE-INFORCED  CONCRETE  BRIDGES 


201 


202     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


iS;  :'"-' 


:ffi 


RE-INFORCED  CONCRETE  BRIDGES 


203 


204     RE-INFORCED    CONCRETE   CONSTRUCTIONS 


REINFORCING    EXISTING     STEEL  BRIDGES 
BY  CONCRETE. 

Existing  steel  bridges  which  show  signs  of  deterior- 
ation or  are  too  weak  for  the  increased  loads  passing 
over  them,  can  be  reinforced  by  concrete  at  often  nom- 
inal expense.  Plate  girder  bridges  can  be  lined  with 
concrete  and  additional  steel  rods  added  to  bottom  and 
top  chords.  Also  cross  girders  and  stringers  can  be 
embedded  in  concrete,  and  a  new  concrete  floor  placed ; 
in  this  wray  a  new  bridge  is  obtained,  which  will  be 
more  sightly  and  substantial  than  the  old  steel  bridge. 
A  good  example  of  such  a  reinforcement  of  a  bridge  is 
shown  in  Fig.  170.  The  lattice  work  of  the  main  gird- 
ers and  the  webs  of  the  cross  girders  were  utterly  cor- 
roded by  sulphurous  gases  and  the  sand  blast  action  of 
locomotives  stopping  under  it. 

A  few  yards  of  concrete,  used  to  embed  the  main  and 
cross  girders  and  to  place  a  substantial  floor,  produced 
a  new  bridge,  which  may  last  indefinitely. 

Trussed  bridges  can  also  be  reinforced  in  a  similar 
way,  embedding  bottom  and  top  chords,  diagonals 
and  verticals,  cross  girders  and  stringers  in  concrete 
and  adding  new  steel  rods  to  increase  the  strength  of 
the  various  members. 

Cement  is  to-day  recognized  as  the  best  preserver  of 
iron  and  steel  against  rust,  and  the  French  railroads 
now  use,  exclusively,  cement  mortar  to  paint  their 

bridges. 

205 


206     RE-INFORCED   CONCRETE   CONSTRUCTIONS 


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Figs.    170-172. — Reinforcing    an    old    steel    bridge    with    con- 
crete. 


REINFORCED  CONCRETE  CONSTRUCTION          207 

The  illustrations  in  these  pages  were  drawn  largely 
from  constructions,  executed  under  French  systems 
of  reinforced  concrete  construction,  both  in  this  coun- 
try and  abroad. 

We  are  also  indebted  to  the  Ferro-Concrete  Con- 
struction Co.,  of  Cincinnati,  for  several  illustrations. 

To-day  there  are  several  hundred  engineers  and  con- 
tractors engaged  in  armored  concrete  construction  in 
Europe  and  the  United  States,  whose  special  sys- 
tems differ  only  slightly  from  each  other,  omitting 
or  inserting  more  or  less  'important  details-,  from  the 
principles  of  construction  heretofore  described. 

During  the  last  few  years,certain  so-called  patent 
bars  with  notches  or  corrugations,  etc.,  have  appeared 
on  the  market,  for  which  extraordinary  claims  have 
been  made  in  respect  to  the  advantages  when  used  as  a 
reinforcing  member.  The  vendors  of  these  patent 
bars  claim  that  the  adhesion  of  the  concrete  to  their 
bars  is  increased  20  to  50  per  cent,  over  round  rods, 
and,  therefore,  the  strength  of  a  beam  or  a  slab  is  in- 
creased in  the  same  ratio,  which  is,  however,  not  war- 
ranted either  in  theory  or  practice.  In  fact  not  one 
in  a  thousand  of  the  existing  structures  are  built  with 
such  patent  bars.  Experiments  on  reinforced 
concrete  bridges  during  the  last  10  years  prove  thac 
the  adhesion  of  concrete  to  plain  steel  rods  increase^ 
with  age,  and  that  there  is  not  the  least  danger 
of  rupturing  the  bond  by  shocks;  and  nearly  20,000 
structures  where  plain  steel  rods  were  used,  prove  that 
plain  steel  rods  take  care  of  all  tjie  stresses  they  are 
subjected  to.  These  patent  bars  are  sold  at  from  three 
to  five  cents  a  pound,  while  plain  steel  rods  to-day  cost 
only  one  and  three-tenths  cents  a  pound.  The  increase 


208     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

of  adhesion  can  be  secured  much  easier  by  simply  in 
creasing  the  number  of  plain  bars  above  that  given  by 
accepted  practice,  and  we  will  obtain  by  this  expedient 
a  stronger  and  less  expensive  beam,  than  where  the 
costly  patent  bars  are  used.  It  is  true,  that  on  first 
consideration,  these  patent  bars  seem  to  be  a  good 
thing;  but  the  writer  is  warranted  in  saying  that  be 
prefers  to  use  three  times  the  amount  of  plain  steel 
rods,  in  a  given  member,  than  to  pay  three  times  the 
price  for  the  patent  bars. 


GENERAL  SPECIFICATIONS.  209 

GENERAL  SPECIFICATIONS  FOR  FEINFORCED   CONCRETE 
CONSTRUCTION. 

The  work  shall  be  completed  in  accordance  with  the 
general  plans,  sections  and  diagrams  submitted  by  the 
concrete  contractor  to  the  architect,  engineer  or  owner. 
The  contractor  must  prove  that  the  plans  are  prepared 
by  competent  engineers  who  have  had  at  least  three 
(3)  years  experience  in  this  line  of  work  with  a  respon- 
sible company.  No  change  shall  be  made  in  the  plans 
either  in  thickness  of  any  member  of  construction 
or  in  size,  or  position  of  steel  rods,  without  written 
permit  from  the  engineer  in  charge  of  the  reinforced 
concrete  construction. 

MATERIALS. 

Only  first  class  Portland  cement  shall  be  used.  Each 
car  load  of  cement  shall  be  tested  and  is  to  conform  to 
the  standard  required  by  the  United  States  Govern- 
ment (see  the  specifications). 

SAND — The  sand  shall  be  clean  and  sharp  and  free 
from  loam  or  other  impurities,  and,  preferably,  a  mix- 
ture of  grains  of  all  sizes  from  1-4  inch  down  to  the 
finest,  if  such  sand  can  be  had  at  reasonable  price. 

CRUSHED  STONE  OR  GRAVEL — Shall  be  free  from 
loam  or  other  impurities,  of  hard  material  and  no 
single  piece  be  larger  than  3-4  inch  for  floors, 
columns,  thin  walls,  or  more  than  I  inch  in  footings. 
The  material  should  contain  all  sizes  from  the  specified 
sizes  down  to  and  including  stone  dust ;  the  percentage 
of  stone  dust  shall  not  exceed  10  per  cent  of  the  crusher 
run. 

CONCRETE — At  least  one  barrel  of  cement  for  each 
cubic  yard  of  concrete  shall  be  used.  The  proportion 


210     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

of  cement  sand,  and  crushed  stone  or  gravel  shall  not 
be  less  than  i  \2. 14  for  columns  or  girders,and  1:2  1-2  15 
for  walls,  floors  and  footings.  Whenever  the 
amount  of  concrete  justifies  the  use  of  a  concrete  mixer, 
machine  mixed  concrete  shall  be  used.  Any  kind  of 
batch  mixer  shall  be  allowed.  The  ingredients  shall 
be  placed  in  the  machine  in  a  dry  state,  and  be 
thoroughly  mixed,  after  which  clean  water  shall  be 
added  and  the  mixing  continued  until  a  uniform  mix- 
ture is  obtained.  Where  the  mixing  is  done  by  hand, 
the  cement  shall  be  thoroughly  mixed  dry  on  a  tight 
platform  of  planks  or  sheet  iron,  then  the  previously 
wetted  stone  shall  be  spread  on  the  mixture  of  sand 
and  cement,  clean  water  added,  and  the  whole  turned 
over  two  or  three  times  until  a  perfectly  uniform  mix- 
ture is  obtained. 

The  mixing  shall  be  done  as  rapidly  as  possible  and 
the  concrete  deposited  in  the  work  without  delay.  The 
concrete  shall  be  mixed  moderately  wet,  so  that  tamp- 
ing is  required  to  bring  water  to  the  surface.  At  no 
time  shall  concrete  be  as  wet  as  to  allow  the  stones  to 
sink  in  the  wheel  barrows,  and  the  cement  and  sand 
and  water  to  rise  toi  the  surface.  The  concrete  may  be 
fairly  wet  for  walls,  which  have  little  to  carry,  so  that 
churning  of  the  concrete  only  is  required  to  get  rid  of 
the  air  drawn  in  by  pouring. 

The  materials  shall  be  measured  loose,  but  in  a  uni- 
form manner,  so  that  the  proportions  can  be  easily 
controlled  by  workmen  and  inspectors.  The  concrete 
shall  be  deposited  in  a  layer  of  a  few  inches,  never 
exceeding  six,  and  rolled  or  rammed  till  the  water  ap- 
pears at  the  surface.  Where  a  complete  section  of  the 
work  joins  a  section  just  being  deposited,  extra  care 
shall  be  taken  that  the  surfaces  are  well  picked  out, 


GENERAL  SPECIFICATIONS. 

and  washed  clean  with  water,  and  well  grouted,  iu 
order  to  make  a  proper  bond  between  the  sections.  This 
applies  especially  to  the  joints  of  columns  with  gird- 
ers, girders  withT  floors,  floors  with  walls,  etc. 

FORMS — The  forms  shall  consist  of  i  to2  inch  boards 
of  uniform  thickness  joined  carefully  together,  straight 
and  true  to  line,  so  that  the  irregularities  in  the  ex- 
posed concrete  surfaces  shall  not  be  greater  than  1-4 
inch.  The  forms  have  to  be  well  braced  and  supported, 
so  that  there  be  no  undue  deflection,  when  the  concrete 
is  deposited. 

The  forms  for  girders  shall  not  be  removed  before 
three  weeks  to  four  weeks,  for  floors  not  before  one 
to  two  weeks,  according  to  the  temperature.  The  sides 
of  columns  and  walls  may  be  removed  in  one  to  two 
days ;  the  surface  has,  however,  to  be  sprinkled  to  pre- 
vent checking  on  account  of  too  rapid  hardening1  of  the 
layers.  This  sprinkling  has  to  be  done  during  warm 
and  dry  weather  and  continued  for  several  days  on 
all  newly  built  concrete,  especially  floors. 

CONCRETING  IN  COLD  WEATHER — Concreting  above 
30  degrees  Fahrenheit  may  be  carried1  on  without  heat- 
ing the  materials.  In  temperatures  above  26  and  below 
30  degrees  F.,  the  cement,  sand  and  water  shall  be 
heated,  and  the  concrete  covered  immediately  by  cloth 
and  a  thick  layer  of  sand.  No  concreting:  of  important 
parts  of  the  work  shall  be  carried  on  below  26  degrees 
F.  The  weather  reports  must  be  consulted  daily  and 
if  a  cold  spell  is  predicted  the  next  12  hours,  work  must 
be  stopped. 

IRON — Shall  have  an  ultimate  tensile  strength  of 
not  less  than  50,000  Ibs.  per  square  inch  ;  and  the  elastic 
limit  shall  not  be  less  than  25,000  Ibs.  It  must  bend 


212     RE-INFORCED   CONCRETE  CONSTRUCTIONS 

cold  1 80  degrees. around  a  rod  whose  diameter  is  equal 
to  the  thickness  of  the  piece  tested,  without  any  sign 
of  failure. 

STEEL — Shall  have  an  ultimate  tensile  strength  of  at 
least  60,000  Ibs.  per  square  inch,  and  an  elastic  limit  of 
not  less  than  half  the  ultimate  tensile  strength.  It  must 
bend  cold  180  degrees  around  a  curve,  whose  diameter 
is  equal  to  the  thickness  of  the  piece  tested,  without 
crack  or  flaw  on  outside  of  bend.  All  iron  or  steel  used 
must  be  free  from  dirt  or  other  impurities,  but  may 
have  a  slight  coat  of  rust,  which  coat  facilitates  the 
forming  of  a  hard  coat  of  ferro  calcite,  and  increases 
the  adhesion  to  the  concrete. 

TESTS — Five  per  cent,  of  all  girders  shall  be  tested 
to  at  least  11-2  times  the  specified  loads  and  the  de- 
flection shall  not  be  greater  than  1-800  of  the  span. 
No  crack  or  other  indication  of  weakness  shall  be  per- 
missible. Any  girder  not  passing  these  tests  shall  be 
rebuilt  in  armored  concrete  or  replaced  by  steel  con- 
struction at  the  discretion  of  the  architect. 


SPECIFICATIONS  FOR  PORTLAND    CEMENT, 
U.  S.  ARMY  CORPS  OF  ENGINEERS. 

The  cement  shall  be  an  American  Portland,  dry  and 
free  from  lumps.  By  a  Portland  cement  is  meant  the 
product  obtained  from  the  heating  or  calcining  up  to 
incipient  fusion  of  intimate  mixtures,  either  natural  or 
artificial,  of  argillaceous  with  calcareous  substances; 
the  calcined  product  should  contain  at  least  1.7  times  as 
much  lime,  by  weight,  as  of  the  materials  which  give 
the  lime  its  hydraulic  properties ;  it  should  be  finely  pul- 
verized after  said  calcination,  and  thereafter  addition 
or  substitution  not  to  exceed  2  per  cent,  of  the  calcined 
products  should  be  allowed,  and  only  for  the  purpose 
of  regulating  certain  properties  of  technical  import- 
ance. 

The  cement  shall  be  put  up  in  strong,  sound  barrels 
well  lined  with  paper,  so  as  to  be  reasonably  protected 
against  moisture,  or  in  stout  cloth  or  canvas  sacks. 
Each  package  shall  be  plainly  labeled  with  the  name 
of  the  brand  and  of  the  manufacturer.  Any  package 
broken  or  containing  damaged  cement  may  be  rejected 
or  accepted  as  a  fractional  package,  at  the  option  of 
the  United  States  agent  in  local  charge. 

No  cement  shall  be  used  except  established  brands 
of  high  grade  Portland  cement  which  have  beeen  made 
by  the  same  mill  and  in  successful  use  under  climatic 
conditions  similar  to  those  of  the  proposed  work  for  at 

least  three  years. 

213 


214     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

The  average  weight  per  barrel  shall  not  be  less  than 
375  pounds  net.  Four  sacks  shall  contain  one  barrel 
of  cement.  If  the  weight,  as  determined  by  test  weigh 
ings,  is  found  to  be  below  375  pounds  per  barrel,  the 
cement  may  be  rejected,  or,  at  the  option  of  the  engin- 
eer of  officer  in  charge,  the  contractor  may  be  required 
to  supply,  free  of  cost  to  the  United  States,  an  addi- 
tional amount  of  cement  equal  to  the  shortage. 

Tests  may  be  made  of  the  fineness,  specific  gravity, 
soundness,  time  of  setting  and  tensile  strength  of  the 
cement. 

FINENESS — Ninety-two  per  cent,  of  the  cement  must 
pass  through  a  sieve  of  No.  40  wire,  Stubb's  gauge, 
having  10,000  openings  per  square  inch. 

SPECIFIC  GRAVITY — The  specific  gravity  of  the  ce- 
ment, as  determined  from  a  sample  which  has  been 
carefully  dried,  shall  be  between  3.10  and  3.25. 

SOUNDNESS — To  test  the  soundness  of  the  cement, 
at  least  two  pats  of  neat  cement  mixed  for  five  minutes 
with  20  per  cent,  of  water  by  weight  shall  be  made  on 
glass,  each  pat  about  three  inches  in  diameter  and  one  • 
half  inch  thick  at  the  center,  tapering  thence  to  a  thin 
edge.  The  pats  are  to  be  kept  under  a  wet  cloth  until 
finally  set,  when  one  is  to  be  placed  in  fresh  water  for 
twenty-eight  days.  The  second  pat  will  be  placed  in 
water  which  will  be  raised  to  the  boiling  point  for 
six  hours,  then  allowed  to  cool.  Neither  should  show 
distortion  or  cracks.  The  boiling  test  may  or  may  not 
reject  at  the  option  of  the  engineer  or  officer  in  charge. 
TIME  OF  SETTING — The  cement  shall  not  acquire  its 
initial  set  in  less  than  forty-five  minutes'  and  must  have 
acquired  its  final  set  in  ten  hours. 


CEMENT  SPECIFICATIONS  215 

(The  following  paragraph  will  be  substituted  for  the 
above  in  case  a  quick-setting  cement  is  desired : 

The  cement  shall  not  acquire  its  initial  set  in  less 
than  twenty  nor  more  than  thirty  minutes,  and  must 
have  acquired  its  final  set  in  not  less  than  forty-five 
minutes,  nor  in  more  than  two  and  one-half  hours.) 

The  pats  made  to  test  the  soundness  may  be  used  in 
determining  the  time  of  setting.  The  cement  is  con- 
sidered to  have  acquired  its  initial  set  when  the  pat 
will  bear,  without  being  appreciably  indented,  a  wire 
one-twelfth  inch  in  diameter  loaded  to  weigh  one- 
fourth  pound.  The  final  set  has  been  acquired  when 
the  pat  wall  bear,  without  being  appreciably  indented, 
a  wire  one-twenty-fourth  inch  in  diameter  loaded  to 
weigh  one  pound 

TENSILE  STRENGTH — Briquettes  made  of  neat  ce- 
ment, after  being  kept  in  air  for  twenty-four  hours 
under  a  wet  cloth,  and  the  balance  of  the  time  in  water, 
shall  develop  tensile  strength  per  square  inch  as  fol- 
lows : 

After  seven  days,  450  pounds;  after  twenty-eight 
days,  540  pounds. 

Briquettes  made  of  i  part  cement  and  3  parts  stand- 
ard sand,  by  weight,  shall  develop  tensile  strength  per 
square  inch  as  follows : 

After  seven  days,  140  pounds ;  after  tenty-eight  days, 
220  pounds. 

(In  case  quick-setting  cement  is  desired,  the  follow- 
ing tensile  strength  shall  be  substituted  for  the  above : 

Neat  briquettes:  After  seven  days,  400  pounds; 
after  twenty-eight  days,  480  pounds. 

Briquettes  of  i  part  cement  to  3  parts  standard 
sand:  After  seven  days,  120  pounds;  after  twenty- 
eight  days,  1 80  pounds.) 


216     RE-INFORCED   CONCRETE   CONSTRUCTIONS 

The  highest  result  from  each  set  of  briquettes  made 
at  any  one  time  is  to  be  considered  the  governing  test. 
Any  cement  not  showing  an  increase  of  strength  in 
the  twenty-eight  day  tests  over  the  seven-day  tests, 
shall  be  rejected. 

When  making  briquettes  neat  cement  will  be  mixed 
with  20  per  cent,  of  water  by  weight,  and  sand  and 
cement  with  121-2  per  cent,  of  water  by  weight.  After 
being  thoroughly  mixed  for  five  minutes,  the  cement  or 
mortar  will  be  placed  in  the  briquette  mold  in  four 
equal  layers,  and  each  layer  rammed  and  compressed 
by  thirty  blows  of  a  soft  brass  or  copper  rammer  three- 
quarters  of  an  inch  in  diameter  (or  seven-tenths  of  an 
inch  square,  with  rounded  corners),  weighing  i  pound. 
It  is  to  be  allowed  to  drop  on  the  mixture  from  a 
height  of  about  half  an  inch.  When  ramming  has 
been  completed,  the  surplus  cement  shall  be  struck  off 
and  the  final  layer  smoothed  with  a  trowel  held  almost 
horizontal  and  drawn  back  with  sufficient  pressure  to 
make  its  edge  follow  the  surface  of  the  mold. 

The  above  are  to  be  considered  the  minimum  require- 
ments. Unless  a  cement  has  been  recently  used  on 
work  under  this  office,  bidders  will  deliver  a  sample 
barrel  for  test  before  the  opening  of  bids.  If  this 
sample  shows  higher  tests  than  those  given  above,  the 
average  of  tests  made  on  subsequent  shipments  must 
come  up  to  those  found  with  the  sample. 

A  cement  may  be  rejected  in  case  it  fails  to  meet 
any  of  the  above  requirements.  An  agent  of  the  con- 
tractor may  be  present  at  the  making  of  the  tests,  or, 
in  case  of  the  failure  of  any  of  them  they  may  be  re- 
peated in  his  presence.  If  the  contractor  so  desires,  the 
engineer  officer  in  charge  may,  if  he  deem  it  to  be  to 


CEMENT  SPECIFICATIONS  217 

the  interest  of  the  United  States,  have  any  or  all  of  the 
tests  made  or  repeated  at  some  recognized  standard 
testing  laboratory  in  the  manner  herein  specified.  All 
expenses  of  such  tests  to  be  paid  by  the  contractor.  All 
such  tests  shall  be  made  on  samples  furnished  by  the 
engineer  officer  from  cement  actually  delivered  to  him. 


*Chas.  W.Stevens  Cast  Stone 


T^ 


With  our  machine,  one  man  can  produce  seven 
standard  building  blocks  in  5  minutes  by  one  opera- 
tion, after  the  Concrete  has  been  mixed,  one  man  then 
removes  the  entire  seven  blocks,  all  together  in  a  sin- 
gle operation,  and  sets  themaside  to  harden. 

This  is  repeated  continuously,  without  intermission. 
Thereby  we  obtain  the  greatest  output  at  the  lowest 
cost.  Our  stone  is  produced  without  tamping  or  pres- 
sure. Is  strong,  durable  and  shows  an  exceedingly  fine 
finish.  For  manufacturing  r'ght  and  descriptive  pamph- 
lets address 


The  Stevens  Cast  Stone  Co. 


L 


808  Chamber  of  Commerce, 

CHICAGO,  ILL.  - 


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